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Plant List
Indexed Alphabetically by Common Name
H, I, J, K
For a list of plants indexed by Scientific Name, click here
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| National Common Name | Scientific Name with Author | Symbol | Family | |
| ha'a | Antidesma platyphyllum Mann | ANPL2 | Euphorbiaceae | |
| ha'a | Antidesma platyphyllum Mann var. platyphyllum | ANPLP | Euphorbiaceae | |
| hackberry | Celtis L. | CELTI | Ulmaceae | |
| Hagen's bryum moss | Bryum hagenii Limpr. | BRHA3 | Bryaceae | |
| haggarbush | Clerodendrum aculeatum (L.) Schlecht. | CLAC2 | Verbenaceae | |
| haha'aiakamanu | Clermontia fauriei Levl. | CLFA | Campanulaceae | |
| hahala | Cyrtandra garnotiana Gaud. | CYGA2 | Gesneriaceae | |
| Haid's amygdalaria lichen | Amygdalaria haidensis Brodo & Hertel | AMHA | Porpidiaceae | |
| hairgrass | Aira L. | AIRA | Poaceae | |
| hairlike sedge | Carex capillaris L. | CACA12 | Cyperaceae | |
| hairpin banksia | Banksia spinulosa Sm. | BASP6 | Proteaceae | |
| hairsedge | Bulbostylis Kunth | BULBO | Cyperaceae | |
| hairy angelica | Angelica venenosa (Greenway) Fern. | ANVE | Apiaceae | |
| hairy arnica | Arnica mollis Hook. | ARMO4 | Asteraceae | |
| hairy ayenia | Ayenia pilosa Cristobal | AYPI | Sterculiaceae | |
| hairy balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. hirsuta (Nutt.) A. Nels. | BAHOH | Asteraceae | |
| hairy balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. hispidula (Sharp) Cronq. | BAHOH2 | Asteraceae | |
| hairy beggarticks | Bidens pilosa L. | BIPI | Asteraceae | |
| hairy bird's beak | Cordylanthus pilosus Gray ssp. pilosus | COPIP | Scrophulariaceae | |
| hairy bird's beak | Cordylanthus pilosus Gray ssp. trifidus (Robins. & Greenm.) Chuang & Heckard | COPIT | Scrophulariaceae | |
| hairy bird's-beak | Cordylanthus pilosus Gray | COPI2 | Scrophulariaceae | |
| hairy bittercress | Cardamine hirsuta L. | CAHI3 | Brassicaceae | |
| hairy bluestem | Andropogon longiberbis Hack. | ANLO2 | Poaceae | |
| hairy brome | Bromus ramosus Huds. | BRRA3 | Poaceae | |
| hairy bugseed | Corispermum villosum Rydb. | COVI5 | Chenopodiaceae | |
| hairy ceanothus | Ceanothus oliganthus Nutt. | CEOL | Rhamnaceae | |
| hairy chaffhead | Carphephorus paniculatus (J.F. Gmel.) Herbert | CAPA53 | Asteraceae | |
| hairy clematis | Clematis hirsutissima Pursh | CLHI | Ranunculaceae | |
| hairy clematis | Clematis hirsutissima Pursh var. hirsutissima | CLHIH | Ranunculaceae | |
| hairy cup orchid | Brachionidium ciliolatum Garay | BRCI4 | Orchidaceae | |
| hairy cyanea | Cyanea pilosa Gray | CYPI4 | Campanulaceae | |
| hairy cyanea | Cyanea pilosa Gray ssp. longipedunculata (Rock) Lammers | CYPIL | Campanulaceae | |
| hairy cyanea | Cyanea pilosa Gray ssp. pilosa | CYPIP | Campanulaceae | |
| hairy dozedaisy | Aphanostephus pilosus Buckl. | APPI | Asteraceae | |
| hairy false cloak fern | Argyrochosma incana (K. Presl) Windham | ARIN11 | Pteridaceae | |
| hairy five eyes | Chamaesaracha sordida (Dunal) Gray | CHSO | Solanaceae | |
| hairy flatsedge | Cyperus dentoniae G. Tucker | CYDE10 | Cyperaceae | |
| hairy flowering fern | Anemia hirsuta (L.) Sw. | ANHI2 | Anemiaceae | |
| hairy grama | Bouteloua hirsuta Lag. | BOHI2 | Poaceae | |
| hairy grama | Bouteloua hirsuta Lag. var. hirsuta | BOHIH | Poaceae | |
| hairy Indian mallow | Abutilon grandifolium (Willd.) Sweet | ABGR3 | Malvaceae | |
| hairy Indian paintbrush | Castilleja tenuis (Heller) Chuang & Heckard | CATE26 | Scrophulariaceae | |
| hairy jointvetch | Aeschynomene villosa Poir. | AEVI2 | Fabaceae | |
| hairy joyweed | Alternanthera flavogrisea Urban | ALFL5 | Amaranthaceae | |
| hairy knight's-spur | Consolida pubescens (DC.) Soó | COPU21 | Ranunculaceae | |
| hairy lady's mantle | Alchemilla monticola Opiz | ALMO4 | Rosaceae | |
| hairy lipfern | Cheilanthes lanosa (Michx.) D.C. Eat. | CHLA2 | Pteridaceae | |
| hairy manzanita | Arctostaphylos columbiana Piper | ARCO3 | Ericaceae | |
| hairy marshmallow | Althaea hirsuta L. | ALHI2 | Malvaceae | |
| hairy mountain mahogany | Cercocarpus montanus Raf. var. paucidentatus (S. Wats.) F.L. Martin | CEMOP | Rosaceae | |
| hairy pagoda-plant | Blephilia hirsuta (Pursh) Benth. | BLHI | Lamiaceae | |
| hairy pagoda-plant | Blephilia hirsuta (Pursh) Benth. var. glabrata Fern. | BLHIG | Lamiaceae | |
| hairy pagoda-plant | Blephilia hirsuta (Pursh) Benth. var. hirsuta | BLHIH | Lamiaceae | |
| hairy ragweed | Ambrosia canescens Gray | AMCA7 | Asteraceae | |
| hairy rockcress | Arabis hirsuta (L.) Scop. | ARHI | Brassicaceae | |
| hairy rockcress | Arabis hirsuta (L.) Scop. var. hirsuta | ARHIH | Brassicaceae | |
| hairy rockrose | Cistus incanus L. | CIIN80 | Cistaceae | |
| hairy rockrose | Cistus incanus L. ssp. corsicus (Loisel.) Heywood | CIINC | Cistaceae | |
| hairy rockrose | Cistus incanus L. ssp. incanus | CIINI | Cistaceae | |
| hairy sandmat | Chamaesyce villifera (Scheele) Small | CHVI17 | Euphorbiaceae | |
| hairy sedge | Carex lacustris Willd. | CALA16 | Cyperaceae | |
| hairy sensitive pea | Chamaecrista pilosa (L.) Greene | CHPI5 | Fabaceae | |
| hairy smotherweed | Bassia hirsuta (L.) Aschers. | BAHI3 | Chenopodiaceae | |
| hairy spotflower | Acmella pilosa R.K. Jansen | ACPI4 | Asteraceae | |
| hairy suncup | Camissonia pubens (S. Wats.) Raven | CAPU15 | Onagraceae | |
| hairy torchwood | Amyris diatrypa Spreng. | AMDI4 | Rutaceae | |
| hairy whitetop | Cardaria pubescens (C.A. Mey.) Jarmolenko | CAPU6 | Brassicaceae | |
| hairy wild cabbage | Caulanthus pilosus S. Wats. | CAPI4 | Brassicaceae | |
| hairy woodland brome | Bromus pubescens Muhl. ex Willd. | BRPU6 | Poaceae | |
| hairyflower bellflower | Campanula chamissonis Fedorov | CACH | Campanulaceae | |
| hairyfruit chervil | Chaerophyllum tainturieri Hook. | CHTA | Apiaceae | |
| hairyfruit chervil | Chaerophyllum tainturieri Hook. var. dasycarpum Hook. ex S. Wats. | CHTAD | Apiaceae | |
| hairyfruit chervil | Chaerophyllum tainturieri Hook. var. tainturieri | CHTAT | Apiaceae | |
| hairyfruit sedge | Carex trichocarpa Muhl. ex Willd. | CATR8 | Cyperaceae | |
| hairy-pod milkvetch | Astragalus concordius Welsh | ASCO61 | Fabaceae | |
| hairyseed bahia | Bahia absinthifolia Benth. | BAAB | Asteraceae | |
| hairyseed bahia | Bahia absinthifolia Benth. var. absinthifolia | BAABA | Asteraceae | |
| hairystem rockcress | Arabis sparsiflora Nutt. var. subvillosa (S. Wats.) Rollins | ARSPS | Brassicaceae | |
| Haitian catalpa | Catalpa longissima (Jacq.) Dum.-Cours. | CALO8 | Bignoniaceae | |
| halberdleaf orach | Atriplex calotheca (Rafn) Fr. | ATCA6 | Chenopodiaceae | |
| Haleakala clermontia | Clermontia tuberculata Forbes | CLTU2 | Campanulaceae | |
| Haleakala cyanea | Cyanea aculeatiflora Rock | CYAC4 | Campanulaceae | |
| Haleakala spleenwort | Asplenium haleakalense W.H. Wagner | ASHA14 | Aspleniaceae | |
| halfmoon milkvetch | Astragalus allochrous Gray | ASAL6 | Fabaceae | |
| halfmoon milkvetch | Astragalus allochrous Gray var. allochrous | ASALA10 | Fabaceae | |
| halfmoon milkvetch | Astragalus allochrous Gray var. playanus Isely | ASALP | Fabaceae | |
| Haller's bartramia moss | Bartramia halleriana Hedw. | BAHA4 | Bartramiaceae | |
| Haller's campylium moss | Campylium halleri (Hedw.) Lindb. | CAHA33 | Amblystegiaceae | |
| Hall's archidium moss | Archidium hallii Aust. | ARHA9 | Archidiaceae | |
| Hall's arthothelium lichen | Arthothelium hallii (Tuck.) Zahlbr. | ARHA7 | Uncertain Lichen Family | |
| Hall's bentgrass | Agrostis hallii Vasey | AGHA2 | Poaceae | |
| Hall's bruchia moss | Bruchia hallii Aust. | BRHA2 | Bruchiaceae | |
| Hall's columbiadoria | Columbiadoria hallii (Gray) Nesom | COHA5 | Asteraceae | |
| Hall's hawksbeard | Crepis runcinata (James) Torr. & Gray ssp. hallii Babcock & Stebbins | CRRUH | Asteraceae | |
| Hall's milkvetch | Astragalus hallii Gray | ASHA2 | Fabaceae | |
| Hall's milkvetch | Astragalus hallii Gray var. fallax (M.E. Jones) Barneby | ASHAF | Fabaceae | |
| Hall's milkvetch | Astragalus hallii Gray var. hallii | ASHAH | Fabaceae | |
| Hall's milkweed | Asclepias hallii Gray | ASHA6 | Asclepiadaceae | |
| Hall's mule-ears | Agnorhiza elata (Hall) W.A. Weber | AGEL8 | Asteraceae | |
| Hall's sedge | Carex halliana Bailey | CAHA2 | Cyperaceae | |
| Hall's suncup | Camissonia pallida (Abrams) Raven ssp. hallii (A. Davids.) Raven | CAPAH2 | Onagraceae | |
| Hall's wild cabbage | Caulanthus hallii Payson | CAHA8 | Brassicaceae | |
| Hamakua clermontia | Clermontia pyrularia Hbd. | CLPY2 | Campanulaceae | |
| hame | Antidesma pulvinatum Hbd. | ANPU2 | Euphorbiaceae | |
| Hamilton's milkvetch | Astragalus hamiltonii C.L. Porter | ASHA3 | Fabaceae | |
| hammer sedge | Carex hirta L. | CAHI10 | Cyperaceae | |
| hammock fern | Blechnum occidentale L. | BLOC | Blechnaceae | |
| hammock sedge | Carex fissa Mackenzie | CAFI5 | Cyperaceae | |
| hammock sedge | Carex fissa Mackenzie var. aristata F.J. Herm. | CAFIA | Cyperaceae | |
| hammock sedge | Carex fissa Mackenzie var. fissa | CAFIF | Cyperaceae | |
| hammock snakeroot | Ageratina jucunda (Greene) Clewell & Woot. | AGJU2 | Asteraceae | |
| Hammond's claytonia | Claytonia virginica L. var. hammondiae (Kalmbacher) Doyle, Lewis & Snyder | CLVIH | Portulacaceae | |
| Hana clermontia | Clermontia samuelii Forbes | CLSA5 | Campanulaceae | |
| Hana clermontia | Clermontia samuelii Forbes ssp. hanaensis (St. John) Lammers | CLSAH2 | Campanulaceae | |
| Hana clermontia | Clermontia samuelii Forbes ssp. samuelii | CLSAS | Campanulaceae | |
| Hana Forest silversword | Argyroxiphium grayanum (Hbd.) O. Deg. | ARGR5 | Asteraceae | |
| hand fern | Cheiroglossa palmata (L.) K. Presl | CHPA14 | Ophioglossaceae | |
| handsome cryptantha | Cryptantha paradoxa (A. Nels.) Payson | CRPA6 | Boraginaceae | |
| handsome sedge | Carex formosa Dewey | CAFO4 | Cyperaceae | |
| hanging sedge | Carex pendula Huds. | CAPE45 | Cyperaceae | |
| hangingpod milkvetch | Astragalus atropubescens Coult. & Fisher | ASAT2 | Fabaceae | |
| Hansen's bird's beak | Cordylanthus pilosus Gray ssp. hansenii (Ferris) Chuang & Heckard | COPIH | Scrophulariaceae | |
| hapu'u | Cibotium glaucum (Sm.) Hook. & Arn. | CIGL | Dicksoniaceae | |
| hapu'u li | Cibotium menziesii Hook. | CIME8 | Dicksoniaceae | |
| Harbison's hawthorn | Crataegus harbisonii Beadle | CRHA2 | Rosaceae | |
| Hardham's evening-primrose | Camissonia hardhamiae Raven | CAHA15 | Onagraceae | |
| hardheads | Acroptilon Cass. | ACROP | Asteraceae | |
| hardheads | Acroptilon repens (L.) DC. | ACRE3 | Asteraceae | |
| hardy swamplily | Crinum bulbispermum (Burm. f.) Milne-Redhead & Schweickerdt | CRBU2 | Liliaceae | |
| harebell | Asyneuma Griseb. & Schenk | ASYNE | Campanulaceae | |
| hare's ear | Bupleurum rotundifolium L. | BURO | Apiaceae | |
| hare's ear mustard | Conringia Heister ex Fabr. | CONRI | Brassicaceae | |
| hare's ear mustard | Conringia orientalis (L.) Dumort. | COOR | Brassicaceae | |
| Harford's sedge | Carex harfordii Mackenzie | CAHA4 | Cyperaceae | |
| harlequin dutchman's pipe | Aristolochia anguicida Jacq. | ARAN6 | Aristolochiaceae | |
| harlequin glorybower | Clerodendrum trichotomum Thunb. | CLTR | Verbenaceae | |
| Harold's milkvetch | Astragalus robbinsii (Oakes) Gray var. harringtonii (Rydb.) Barneby | ASROH | Fabaceae | |
| Harper's dodder | Cuscuta harperi Small | CUHA | Cuscutaceae | |
| Harper's searocket | Cakile edentula (Bigelow) Hook. ssp. harperi (Small) Rodman | CAEDH | Brassicaceae | |
| Harper's sedge | Carex leptalea Wahlenb. ssp. harperi (Fern.) W. Stone | CALEH | Cyperaceae | |
| Harrington's cephalotaxus | Cephalotaxus harringtonia (Knight ex Forbes) K. Koch | CEHA2 | Cephalotaxaceae | |
| Harris' dwarf sand verbena | Abronia nana S. Wats. var. harrisii Welsh | ABNAH | Nyctaginaceae | |
| Harrison's barberry | Berberis harrisoniana Kearney & Peebles | BEHA2 | Berberidaceae | |
| Harrison's milkvetch | Astragalus harrisonii Barneby | ASHA4 | Fabaceae | |
| harsh cyanea | Cyanea scabra Hbd. | CYSC7 | Campanulaceae | |
| harsh Indian paintbrush | Castilleja hispida Benth. | CAHI9 | Scrophulariaceae | |
| harsh Indian paintbrush | Castilleja hispida Benth. ssp. hispida | CAHIH2 | Scrophulariaceae | |
| Hart's tonguefern | Asplenium scolopendrium L. | ASSC11 | Aspleniaceae | |
| Hart's tonguefern | Asplenium scolopendrium L. var. americanum (Fern.) Kartesz & Gandhi | ASSCA | Aspleniaceae | |
| Hartweg's cyphomandra | Cyphomandra hartwegii (Miers) Dunal | CYHA12 | Solanaceae | |
| Hartweg's milkvetch | Astragalus hartwegii Benth. | ASHA5 | Fabaceae | |
| Hartweg's spineflower | Chorizanthe pungens Benth. var. hartwegiana Reveal & Hardham | CHPUH2 | Polygonaceae | |
| Hartweg's sundrops | Calylophus hartwegii (Benth.) Raven | CAHA14 | Onagraceae | |
| Hartweg's sundrops | Calylophus hartwegii (Benth.) Raven ssp. fendleri (Gray) Towner & Raven | CAHAF | Onagraceae | |
| Hartweg's sundrops | Calylophus hartwegii (Benth.) Raven ssp. filifolius (Eastw.) Towner & Raven | CAHAF2 | Onagraceae | |
| Hartweg's sundrops | Calylophus hartwegii (Benth.) Raven ssp. hartwegii | CAHAH | Onagraceae | |
| Hartweg's sundrops | Calylophus hartwegii (Benth.) Raven ssp. pubescens (Gray) Towner & Raven | CAHAP | Onagraceae | |
| Hartweg's wildginger | Asarum hartwegii S. Wats. | ASHA | Aristolochiaceae | |
| harvest brodiaea | Brodiaea elegans Hoover | BREL | Liliaceae | |
| harvest brodiaea | Brodiaea elegans Hoover ssp. elegans | BRELE | Liliaceae | |
| harvestlice | Agrimonia parviflora Ait. | AGPA6 | Rosaceae | |
| Harvey's hawthorn | Crataegus harveyana Sarg. | CRHA4 | Rosaceae | |
| Harwood's milkvetch | Astragalus insularis Kellogg var. harwoodii Munz & McBurney | ASINH | Fabaceae | |
| haspan flatsedge | Cyperus haspan L. | CYHA | Cyperaceae | |
| Hasse's cracked lichen | Acarospora hassei Herre | ACHA3 | Acarosporaceae | |
| Hassler's alternanthera | Alternanthera hassleriana Chodat ex Chodat & Hassler | ALHA3 | Amaranthaceae | |
| Haussknecht's atrichum moss | Atrichum haussknechtii Jur. & Milde | ATHA4 | Polytrichaceae | |
| Havana snakeroot | Ageratina havanensis (Kunth) King & H.E. Robins. | AGHA4 | Asteraceae | |
| Havard's century plant | Agave havardiana Trel. | AGHA | Agavaceae | |
| Havard's false willow | Baccharis havardii Gray | BAHA2 | Asteraceae | |
| Havard's threeawn | Aristida havardii Vasey | ARHA3 | Poaceae | |
| Hawai'i alectryon | Alectryon macrococcus Radlk. | ALMA | Sapindaceae | |
| Hawai'i alectryon | Alectryon macrococcus Radlk. var. auwahiensis G. Linney | ALMAA | Sapindaceae | |
| Hawai'i alectryon | Alectryon macrococcus Radlk. var. macrococcus | ALMAM2 | Sapindaceae | |
| Hawai'i beggarticks | Bidens hawaiensis Gray | BIHA | Asteraceae | |
| Hawai'i bentgrass | Agrostis sandwicensis Hbd. | AGSA3 | Poaceae | |
| Hawai'I birdnest fern | Asplenium nidus L. | ASNI | Aspleniaceae | |
| Hawai'i chaff flower | Achyranthes atollensis St. John | ACAT | Amaranthaceae | |
| Hawai'i cyrtandra | Cyrtandra hawaiensis C.B. Clarke | CYHA4 | Gesneriaceae | |
| Hawai'i dogweed | Bobea sandwicensis (Gray) Hbd. | BOSA2 | Rubiaceae | |
| Hawai'i false nettle | Boehmeria grandis (Hook. & Arn.) Heller | BOGR3 | Urticaceae | |
| Hawai'i jeweled orchid | Anoectochilus sandvicensis Lindl. | ANSA2 | Orchidaceae | |
| Hawai'i kauilatree | Alphitonia ponderosa Hbd. | ALPO3 | Rhamnaceae | |
| Hawai'i lady's nightcap | Bonamia menziesii Gray | BOME2 | Convolvulaceae | |
| Hawai'I lopleaf | Cypholophus moluccanus (Blume) Miq. | CYMO12 | Urticaceae | |
| Hawai'i mirrorplant | Coprosma cymosa Hbd. | COCY3 | Rubiaceae | |
| Hawai'i pearls | Caesalpinia major (Medik.) Dandy & Exell | CAMA21 | Fabaceae | |
| Hawai'i sedge | Carex alligata Boott | CAAL12 | Cyperaceae | |
| Hawai'i silversword | Argyroxiphium sandwicense DC. | ARSA5 | Asteraceae | |
| Hawai'i silversword | Argyroxiphium sandwicense DC. ssp. macrocephalum (Gray) Mérat | ARSAM | Asteraceae | |
| Hawai'i silversword | Argyroxiphium sandwicense DC. ssp. sandwicense | ARSAS | Asteraceae | |
| hawksbeard | Crepis L. | CREPI | Asteraceae | |
| Haworth's aeonium | Aeonium haworthii Webb & Berth. | AEHA2 | Crassulaceae | |
| hawthorn | Crataegus L. | CRATA | Rosaceae | |
| hawthorn | Crataegus paludosa Sarg. | CRPA24 | Rosaceae | |
| hay sedge | Carex argyrantha Tuckerman | CAAR4 | Cyperaceae | |
| Hayden's Indian paintbrush | Castilleja haydenii (Gray) Cockerell | CAHA16 | Scrophulariaceae | |
| Hayden's milkvetch | Astragalus bisulcatus (Hook.) Gray var. haydenianus (Gray) Barneby | ASBIH | Fabaceae | |
| Hayden's sedge | Carex haydenii Dewey | CAHA7 | Cyperaceae | |
| hazel alder | Alnus serrulata (Ait.) Willd. | ALSE2 | Betulaceae | |
| hazel dodder | Cuscuta coryli Engelm. | CUCO3 | Cuscutaceae | |
| hazelnut | Corylus L. | CORYL | Betulaceae | |
| head sandmat | Chamaesyce capitellata (Engelm.) Millsp. | CHCA29 | Euphorbiaceae | |
| headachevine | Clematis microphylla DC. | CLMI8 | Ranunculaceae | |
| heal and draw | Chaptalia nutans (L.) Polak. | CHNU2 | Asteraceae | |
| healing croton | Croton argyranthemus Michx. | CRAR2 | Euphorbiaceae | |
| Hearst Ranch buckbrush | Ceanothus hearstiorum Hoover & J.B. Roof | CEHE2 | Rhamnaceae | |
| Hearst's manzanita | Arctostaphylos hookeri G. Don ssp. hearstiorum (Hoover & J.B. Roof) P.V. Wells | ARHOH | Ericaceae | |
| heart of Jesus | Caladium bicolor (Ait.) Vent. | CABI11 | Araceae | |
| heartleaf arnica | Arnica cordifolia Hook. | ARCO9 | Asteraceae | |
| heartleaf bittercress | Cardamine cordifolia Gray | CACO6 | Brassicaceae | |
| heartleaf bittercress | Cardamine cordifolia Gray var. cordifolia | CACOC | Brassicaceae | |
| heartleaf bittercress | Cardamine cordifolia Gray var. incana Gray ex M.E. Jones | CACOI | Brassicaceae | |
| heartleaf bittercress | Cardamine cordifolia Gray var. lyallii (S. Wats.) A. Nels. & J.F. Macbr. | CACOL4 | Brassicaceae | |
| heartleaf cyrtandra | Cyrtandra cordifolia Gaud. | CYCO9 | Gesneriaceae | |
| heartleaf iceplant | Aptenia cordifolia (L. f.) Schwant. | APCO | Aizoaceae | |
| heartleaf madeiravine | Anredera cordifolia (Ten.) Steenis | ANCO6 | Basellaceae | |
| heartleaf milkweed | Asclepias cordifolia (Benth.) Jepson | ASCO | Asclepiadaceae | |
| heartleaf peppervine | Ampelopsis cordata Michx. | AMCO2 | Vitaceae | |
| heartleaf sandmat | Chamaesyce cordifolia (Ell.) Small | CHCO11 | Euphorbiaceae | |
| heartleaf springbeauty | Claytonia cordifolia S. Wats. | CLCO3 | Portulacaceae | |
| heartleaf suncup | Camissonia cardiophylla (Torr.) Raven | CACA34 | Onagraceae | |
| heartleaf suncup | Camissonia cardiophylla (Torr.) Raven ssp. cardiophylla | CACAC9 | Onagraceae | |
| heartleaf suncup | Camissonia cardiophylla (Torr.) Raven ssp. robusta (Raven) Raven | CACAR2 | Onagraceae | |
| heartleaf thorn-mint | Acanthomintha obovata Jepson ssp. cordata Jokerst | ACOBC | Lamiaceae | |
| hearts entangled | Ceropegia woodii Schltr. | CEWO | Asclepiadaceae | |
| heartscale | Atriplex cordulata Jepson | ATCO2 | Chenopodiaceae | |
| heartseed | Cardiospermum microcarpum Kunth | CAMI21 | Sapindaceae | |
| heath false brome | Brachypodium pinnatum (L.) Beauv. | BRPI | Poaceae | |
| heath sedge | Carex flacca Schreb. | CAFL8 | Cyperaceae | |
| heath wrightwort | Carlowrightia linearifolia (Torr.) Gray | CALI2 | Acanthaceae | |
| heather | Calluna Salisb. | CALLU | Ericaceae | |
| heather | Calluna vulgaris (L.) Hull | CAVU | Ericaceae | |
| heath-leaf banksia | Banksia ericifolia L. f. | BAER | Proteaceae | |
| heatloving cracked lichen | Acarospora thermophila Herre | ACTH6 | Acarosporaceae | |
| heavy sedge | Carex gravida Bailey | CAGR4 | Cyperaceae | |
| heavy sedge | Carex gravida Bailey var. gravida | CAGRG2 | Cyperaceae | |
| heavy sedge | Carex gravida Bailey var. lunelliana (Mackenzie) F.J. Herm. | CAGRL | Cyperaceae | |
| Heckard's Indian paintbrush | Castilleja montigena Heckard | CAMO20 | Scrophulariaceae | |
| hedge bamboo | Bambusa multiplex (Lour.) Raeusch. ex J.A. & J.H. Schultes | BAMU2 | Poaceae | |
| hedge cactus | Cereus hildmannianus K. Schum. | CEHI3 | Cactaceae | |
| hedge false bindweed | Calystegia sepium (L.) R. Br. | CASE13 | Convolvulaceae | |
| hedge false bindweed | Calystegia sepium (L.) R. Br. ssp. americana (Sims) Brummitt | CASEA2 | Convolvulaceae | |
| hedge false bindweed | Calystegia sepium (L.) R. Br. ssp. angulata Brummitt | CASEA3 | Convolvulaceae | |
| hedge false bindweed | Calystegia sepium (L.) R. Br. ssp. erratica Brummitt | CASEE | Convolvulaceae | |
| hedge false bindweed | Calystegia sepium (L.) R. Br. ssp. limnophila (Greene) Brummitt | CASEL | Convolvulaceae | |
| hedge false bindweed | Calystegia sepium (L.) R. Br. ssp. sepium | CASES | Convolvulaceae | |
| hedge maple | Acer campestre L. | ACCA5 | Aceraceae | |
| hedgehog gourd | Cucumis dipsaceus C.G. Ehrenb. ex Spach | CUDI2 | Cucurbitaceae | |
| hedgehog pricklypoppy | Argemone squarrosa Greene | ARSQ | Papaveraceae | |
| hedgehog pricklypoppy | Argemone squarrosa Greene ssp. glabrata G.B. Ownbey | ARSQG | Papaveraceae | |
| hedgehog pricklypoppy | Argemone squarrosa Greene ssp. squarrosa | ARSQS | Papaveraceae | |
| Heimburger's anemone | Anemone drummondii S. Wats. ssp. heimburgeri A.& D. Löve | ANDRH | Ranunculaceae | |
| Heinemann's andreaea moss | Andreaea heinemannii Hampe & C. Müll. | ANHE10 | Andreaeaceae | |
| helecho gigante | Cyathea tenera (J. Sm. ex Hook.) T. Moore | CYTE10 | Cyatheaceae | |
| helecho gigante de la sierra | Alsophila bryophila R. Tryon | ALBR4 | Cyatheaceae | |
| Heller's bird's-beak | Cordylanthus kingii S. Wats. ssp. helleri (Ferris) Chuang & Heckard | COKIH | Scrophulariaceae | |
| Heller's sedge | Carex helleri Mackenzie | CAHE6 | Cyperaceae | |
| helmet orchid | Cranichis Sw. | CRANI | Orchidaceae | |
| hemlock dwarf mistletoe | Arceuthobium tsugense (Rosendahl) G.N. Jones | ARTS | Viscaceae | |
| hemlock dwarf mistletoe | Arceuthobium tsugense (Rosendahl) G.N. Jones ssp. mertensianae Hawksworth & Nickrent | ARTSM2 | Viscaceae | |
| hemlock dwarf mistletoe | Arceuthobium tsugense (Rosendahl) G.N. Jones ssp. tsugense | ARTST2 | Viscaceae | |
| hemlockparsley | Conioselinum Hoffmann | CONIO | Apiaceae | |
| hemp | Cannabis L. | CANNA | Cannabaceae | |
| Henderson's angelica | Angelica hendersonii Coult. & Rose | ANHE | Apiaceae | |
| Henderson's bentgrass | Agrostis hendersonii A.S. Hitchc. | AGHE3 | Poaceae | |
| Henderson's milkvetch | Astragalus accidens S. Wats. var. hendersonii M.E. Jones | ASACH | Fabaceae | |
| Henderson's needlegrass | Achnatherum hendersonii (Vasey) Barkworth | ACHE10 | Poaceae | |
| Henderson's sedge | Carex hendersonii Bailey | CAHE7 | Cyperaceae | |
| henequen | Agave fourcroydes Lemaire | AGFO2 | Agavaceae | |
| Henry Indian paintbrush | Castilleja parviflora Bong. var. oreopola (Greenm.) Ownbey | CAPAO | Scrophulariaceae | |
| hen's eyes | Ardisia crenata Sims | ARCR80 | Myrsinaceae | |
| Henson's calammophila | ×Calammophila don-hensonii Reznicek & E.J. Judziewicz [Ammophila breviligulata × Calamagrostis canadensis] | CADO7 | Poaceae | |
| Hepburn's sedge | Carex nardina Fries var. hepburnii (Boott) Kükenth. | CANAH | Cyperaceae | |
| Hepp's cracked lichen | Acarospora heppii (Nageli ex Hepp) Nageli ex Korber | ACHE6 | Acarosporaceae | |
| herb of Gilead | Cedronella canariensis (L.) Willd. ex Webb & Berth. | CECA | Lamiaceae | |
| herb of grace | Bacopa monnieri (L.) Pennell | BAMO | Scrophulariaceae | |
| herbert river cherry | Antidesma dallachyanum Baillon | ANDA2 | Euphorbiaceae | |
| Herbst's sandmat | Chamaesyce herbstii W.L. Wagner | CHHE3 | Euphorbiaceae | |
| Herbst's sedge | Carex wahuensis C.A. Mey. ssp. herbstii T. Koyama | CAWAH | Cyperaceae | |
| hermaphrodite flatsedge | Cyperus hermaphroditus (Jacq.) Standl. | CYHE2 | Cyperaceae | |
| hermit milkvetch | Astragalus eremiticus Sheldon | ASER4 | Fabaceae | |
| Hesse's pussypaws | Cistanthe parryi (Gray) Hershkovitz var. hesseae (Thomas) Kartesz & Gandhi | CIPAH | Portulacaceae | |
| Heufler's cracked lichen | Acarospora heufleriana Korber | ACHE7 | Acarosporaceae | |
| hians goosefoot | Chenopodium hians Standl. | CHHI | Chenopodiaceae | |
| Hickman's onion | Allium hickmanii Eastw. | ALHI | Liliaceae | |
| hickory | Carya Nutt. | CARYA | Juglandaceae | |
| hiddenpetal Indian mallow | Abutilon eremitopetalum Caum | ABER | Malvaceae | |
| Higgins' milkvetch | Astragalus lentiginosus Dougl. ex Hook. var. higginsii Welsh & Thorne | ASLEH | Fabaceae | |
| Higgins' springparsley | Cymopterus acaulis (Pursh) Raf. var. higginsii (Welsh) Goodrich | CYACH | Apiaceae | |
| higuerito | Crescentia linearifolia Miers | CRLI5 | Bignoniaceae | |
| higuero de sierra | Crescentia portoricensis Britt. | CRPO6 | Bignoniaceae | |
| Hilgard's suncup | Camissonia hilgardii (Greene) Raven | CAHI12 | Onagraceae | |
| Hill Country silverbush | Argythamnia aphoroides Muell.-Arg. | ARAP | Euphorbiaceae | |
| hill suncup | Camissonia graciliflora (Hook. & Arn.) Raven | CAGR14 | Onagraceae | |
| Hillebrand's flatsedge | Cyperus hillebrandii Boeckl. | CYHI | Cyperaceae | |
| Hillebrand's flatsedge | Cyperus hillebrandii Boeckl. var. decipiens (Hbd.) Kükenth. | CYHID | Cyperaceae | |
| Hillebrand's flatsedge | Cyperus hillebrandii Boeckl. var. hillebrandii | CYHIH2 | Cyperaceae | |
| Hillebrand's ha'a | Antidesma platyphyllum Mann var. hillebrandii Pax & K. Hoffmann | ANPLH2 | Euphorbiaceae | |
| Hillegrand's reedgrass | Calamagrostis hillebrandii (Munro ex Hbd.) A.S. Hitchc. | CAHI | Poaceae | |
| Hillman's silverscale | Atriplex hillmanii (M.E. Jones) Standley | ATHI | Chenopodiaceae | |
| Hillman's stinkweed | Cleomella hillmanii A. Nels. | CLHI2 | Capparaceae | |
| Hill's thistle | Cirsium hillii (Canby) Fern. | CIHI | Asteraceae | |
| hillside clermontia | Clermontia lindseyana Rock | CLLI3 | Campanulaceae | |
| hillside false bindweed | Calystegia subacaulis Hook. & Arn. | CASU19 | Convolvulaceae | |
| hillside false bindweed | Calystegia subacaulis Hook. & Arn. ssp. episcopalis Brummitt | CASUE | Convolvulaceae | |
| hillside false bindweed | Calystegia subacaulis Hook. & Arn. ssp. subacaulis | CASUS2 | Convolvulaceae | |
| hillside milkvetch | Astragalus collinus (Hook.) Dougl. ex G. Don | ASCO7 | Fabaceae | |
| hillside milkvetch | Astragalus collinus (Hook.) Dougl. ex G. Don var. collinus | ASCOC7 | Fabaceae | |
| hilly sandwort | Arenaria benthamii Fenzl ex Torr. & Gray | ARBE | Caryophyllaceae | |
| hillyhock | Callaeum ?macropterum (DC.) D.M. Johnson | CAMA45 | Malpighiaceae | |
| Himalayan cypress | Cupressus torulosa D. Don | CUTO2 | Cupressaceae | |
| Himalayan foothill borinda | Borinda fungosa (T.P. Yi) C.M.A. Stapleton | BOFU | Poaceae | |
| Himalayan hazelnut | Corylus ferox Wallich | COFE5 | Betulaceae | |
| Himalayan hazelnut | Corylus ferox Wallich var. ferox | COFEF | Betulaceae | |
| Hinckley's brickellbush | Brickellia hinckleyi Standl. | BRHI4 | Asteraceae | |
| Hinckley's brickellbush | Brickellia hinckleyi Standl. var. hinckleyi | BRHIH | Asteraceae | |
| Hinckley's golden columbine | Aquilegia chrysantha Gray var. hinckleyana (Munz) Lott | AQCHH | Ranunculaceae | |
| hinoki false cypress | Chamaecyparis obtusa (Siebold & Zucc.) Siebold & Zucc. ex Endl. | CHOB8 | Cupressaceae | |
| hirsute artocarpus | Artocarpus hirsutus Lam. | ARHI7 | Moraceae | |
| hirsute sedge | Carex complanata Torr. & Hook. | CACO9 | Cyperaceae | |
| hispanic crambe | Crambe hispanica L. | CRHI6 | Brassicaceae | |
| Hispaniolan spleenwort | Asplenium sessilifolium Desv. | ASSE11 | Aspleniaceae | |
| hispid agrestia lichen | Agrestia hispida (Mereschk.) Hale & Culb. | AGHI60 | Hymeneliaceae | |
| hispid bird's-beak | Cordylanthus mollis Gray ssp. hispidus (Pennell) Chuang & Heckard | COMOH | Scrophulariaceae | |
| hispid campylium moss | Campylium hispidulum (Brid.) Mitt. | CAHI70 | Amblystegiaceae | |
| hispid needle lichen | Chaenotheca hispidula (Ach.) Zahlbr. | CHHI11 | Coniocybaceae | |
| hispid starburr | Acanthospermum hispidum DC. | ACHI | Asteraceae | |
| Hitchcock's sedge | Carex hitchcockiana Dewey | CAHI8 | Cyperaceae | |
| hoary alyssum | Berteroa incana (L.) DC. | BEIN2 | Brassicaceae | |
| hoary balsamroot | Balsamorhiza incana Nutt. | BAIN | Asteraceae | |
| hoary bowlesia | Bowlesia incana Ruiz & Pavón | BOIN3 | Apiaceae | |
| hoary brome | Bromus subvelutinus Shear | BRSU4 | Poaceae | |
| hoary caper | Capparis incana Kunth | CAIN21 | Capparaceae | |
| hoary hawthorn | Crataegus lanata Beadle | CRLA9 | Rosaceae | |
| hoary manzanita | Arctostaphylos canescens Eastw. | ARCA5 | Ericaceae | |
| hoary manzanita | Arctostaphylos canescens Eastw. ssp. canescens | ARCAC7 | Ericaceae | |
| hoary sandmat | Chamaesyce lata (Engelm.) Small | CHLA10 | Euphorbiaceae | |
| hoaryleaf ceanothus | Ceanothus crassifolius Torr. | CECR | Rhamnaceae | |
| Hobdy's spleenwort | Asplenium hobdyi W.H. Wagner | ASHO8 | Aspleniaceae | |
| Hoffmann's cryptantha | Cryptantha hoffmannii I.M. Johnston | CRHO2 | Boraginaceae | |
| Hoffmann's rockcress | Arabis hoffmannii (Munz) Rollins | ARHO | Brassicaceae | |
| Hoffmann's teddybear cholla | Cylindropuntia ×fosbergii (C.B. Wolf) Backeberg [bigelovii × echinocarpa] | CYFO4 | Cactaceae | |
| hogpeanut | Amphicarpaea Ell. ex Nutt. | AMPHI4 | Fabaceae | |
| hogwort | Croton capitatus Michx. | CRCA6 | Euphorbiaceae | |
| hogwort | Croton capitatus Michx. var. capitatus | CRCAC2 | Euphorbiaceae | |
| Holboell's rockcress | Arabis holboellii Hornem. | ARHO2 | Brassicaceae | |
| Holboell's rockcress | Arabis holboellii Hornem. var. pinetorum (Tidestrom) Rollins | ARHOP3 | Brassicaceae | |
| holio | Cryptocarya mannii Hbd. | CRMA8 | Lauraceae | |
| hollowheart | Acnistus arborescens (L.) Schlecht. | ACAR | Solanaceae | |
| hollyberry cotoneaster | Cotoneaster bullatus Boiss. | COBU4 | Rosaceae | |
| hollyfern | Arachniodes Blume | ARACH2 | Dryopteridaceae | |
| hollyhock | Alcea L. | ALCEA | Malvaceae | |
| hollyhock | Alcea rosea L. | ALRO3 | Malvaceae | |
| hollyleaf burr ragweed | Ambrosia ilicifolia (Gray) Payne | AMIL2 | Asteraceae | |
| hollyleaf ceanothus | Ceanothus purpureus Jepson | CEPU2 | Rhamnaceae | |
| Holm sedge | Carex heteroneura W. Boott var. chalciolepis (Holm) F.J. Herm. | CAHEC | Cyperaceae | |
| Holmes' hawthorn | Crataegus holmesiana Ashe | CRHO5 | Rosaceae | |
| Holm's reedgrass | Calamagrostis holmii Lange | CAHO | Poaceae | |
| Holzinger's brachythecium moss | Brachythecium holzingeri (Grout) Grout | BRHO4 | Brachytheciaceae | |
| honewort | Cryptotaenia DC. | CRYPT5 | Apiaceae | |
| honeycombhead | Balduina Nutt. | BALDU | Asteraceae | |
| honeyvine | Cynanchum laeve (Michx.) Pers. | CYLA | Asclepiadaceae | |
| Honolulu cyanea | Cyanea acuminata (Gaud.) Hbd. | CYAC5 | Campanulaceae | |
| Honolulu lacefern | Ctenitis honolulensis (Hook.) Copeland | CTHO | Dryopteridaceae | |
| Hood River milkvetch | Astragalus hoodianus T.J. Howell | ASHO | Fabaceae | |
| hooded coralroot | Corallorhiza striata Lindl. | COST19 | Orchidaceae | |
| hooded coralroot | Corallorhiza striata Lindl. var. striata | COSTS3 | Orchidaceae | |
| hooded windmill grass | Chloris cucullata Bisch. | CHCU2 | Poaceae | |
| Hood's sedge | Carex hoodii Boott | CAHO5 | Cyperaceae | |
| Hooker's balsamroot | Balsamorhiza hookeri (Hook.) Nutt. | BAHO | Asteraceae | |
| Hooker's balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. hookeri | BAHOH3 | Asteraceae | |
| Hooker's ceanothus | Ceanothus velutinus Dougl. ex Hook. var. hookeri M.C. Johnston | CEVEH2 | Rhamnaceae | |
| Hooker's desert sandwort | Arenaria hookeri Nutt. ssp. desertorum (Maguire) W.A. Weber | ARHOD | Caryophyllaceae | |
| Hooker's manzanita | Arctostaphylos hookeri G. Don | ARHO3 | Ericaceae | |
| Hooker's manzanita | Arctostaphylos hookeri G. Don ssp. hookeri | ARHOH4 | Ericaceae | |
| Hooker's sandwort | Arenaria hookeri Nutt. | ARHO4 | Caryophyllaceae | |
| Hooker's sandwort | Arenaria hookeri Nutt. ssp. hookeri | ARHOH3 | Caryophyllaceae | |
| Hooker's sandwort | Arenaria hookeri Nutt. ssp. pinetorum (A. Nels.) W.A. Weber | ARHOP | Caryophyllaceae | |
| Hooker's scratchdaisy | Croptilon hookerianum (Torr. & Gray) House | CRHO7 | Asteraceae | |
| Hooker's scratchdaisy | Croptilon hookerianum (Torr. & Gray) House var. graniticum (E.B. Sm.) E.B. Sm. | CRHOG | Asteraceae | |
| Hooker's scratchdaisy | Croptilon hookerianum (Torr. & Gray) House var. hookerianum | CRHOH | Asteraceae | |
| Hooker's scratchdaisy | Croptilon hookerianum (Torr. & Gray) House var. validum (Rydb.) E.B. Sm. | CRHOV | Asteraceae | |
| Hooker's sedge | Carex hookeriana Dewey | CAHO7 | Cyperaceae | |
| hooky grass | Ancistrachne uncinulata (R. Br.) S. T. Blake | ANUN4 | Poaceae | |
| Hoover's bentgrass | Agrostis hooveri Swallen | AGHO | Poaceae | |
| Hoover's brodiaea | Brodiaea elegans Hoover ssp. hooveri Niehaus | BRELH | Liliaceae | |
| Hoover's cryptantha | Cryptantha hooveri I.M. Johnston | CRHO4 | Boraginaceae | |
| Hoover's manzanita | Arctostaphylos hooveri P.V. Wells | ARHO7 | Ericaceae | |
| Hoover's sandmat | Chamaesyce hooveri (L.C. Wheeler) Koutnik | CHHO3 | Euphorbiaceae | |
| Hoover's western rosinweed | Calycadenia hooveri G.D. Carr | CAHO18 | Asteraceae | |
| hop sedge | Carex lupulina Muhl. ex Willd. | CALU4 | Cyperaceae | |
| hophead Philippine violet | Barleria lupulina Lindl. | BALU2 | Acanthaceae | |
| Hopi milkvetch | Astragalus fucatus Barneby | ASFU2 | Fabaceae | |
| Hoppner's sedge | Carex subspathacea Wormsk. ex Hornem. | CASU8 | Cyperaceae | |
| horehound | Ballota L. | BALLO | Lamiaceae | |
| horizontal woody rockcress | Arabis suffrutescens S. Wats. var. horizontalis (Greene) Rollins | ARSUH | Brassicaceae | |
| horn loco milkvetch | Astragalus missouriensis Nutt. var. mimetes Barneby | ASMIM | Fabaceae | |
| hornbeam | Carpinus L. | CARPI | Betulaceae | |
| Horn's milkvetch | Astragalus hornii Gray | ASHO2 | Fabaceae | |
| hornwort | Anthoceros L. emend. Prosk. | ANTHO3 | Anthocerotaceae | |
| hornwort | Ceratophyllum L. | CERAT | Ceratophyllaceae | |
| horse chestnut | Aesculus hippocastanum L. | AEHI | Hippocastanaceae | |
| horsebalm | Collinsonia L. | COLLI2 | Lamiaceae | |
| horseflyweed | Baptisia tinctoria (L.) R. Br. ex Ait. f. | BATI | Fabaceae | |
| horsehair lichen | Bryoria Brodo & D. Hawksw. | BRYOR2 | Parmeliaceae | |
| horsehair lichen | Bryoria capillaris (Ach.) Brodo & D. Hawksw. | BRCA14 | Parmeliaceae | |
| horsehair lichen | Bryoria cervinula Mot. ex Brodo & D. Hawksw. | BRCE | Parmeliaceae | |
| horsehair lichen | Bryoria chalybeiformis (L.) Brodo & D. Hawksw. | BRCH60 | Parmeliaceae | |
| horsehair lichen | Bryoria friabilis Brodo & D. Hawksw. | BRFR6 | Parmeliaceae | |
| horsehair lichen | Bryoria furcellata (Fr.) Brodo & D. Hawksw. | BRFU3 | Parmeliaceae | |
| horsehair lichen | Bryoria fuscescens (Gyelnik) Brodo & D. Hawksw. | BRFU60 | Parmeliaceae | |
| horsehair lichen | Bryoria implexa (Hoffm.) Brodo & D. Hawksw. | BRIM | Parmeliaceae | |
| horsehair lichen | Bryoria lanestris (Ach.) Brodo & D. Hawksw. | BRLA60 | Parmeliaceae | |
| horsehair lichen | Bryoria nitidula (Th. Fr.) Brodo & D. Hawksw. | BRNI60 | Parmeliaceae | |
| horsehair lichen | Bryoria pseudocapillaris Brodo & D. Hawksw. | BRPS4 | Parmeliaceae | |
| horsehair lichen | Bryoria pseudofuscescens (Gyelnik) Brodo & D. Hawksw. | BRPS60 | Parmeliaceae | |
| horsehair lichen | Bryoria salazinica Brodo & D. Hawksw. | BRSA2 | Parmeliaceae | |
| horsehair lichen | Bryoria simplicior (Vainio) Brodo & D. Hawksw. | BRSI60 | Parmeliaceae | |
| horsehair lichen | Bryoria spiralifera Brodo & D. Hawksw. | BRSP5 | Parmeliaceae | |
| horsehair lichen | Bryoria subcana (Nyl. ex Stizenb.) Brodo & D. Hawksw. | BRSU6 | Parmeliaceae | |
| horsehair lichen | Bryoria tenuis (E. Dahl) Brodo & D. Hawksw. | BRTE60 | Parmeliaceae | |
| horsehair lichen | Bryoria trichodes (Michaux) Brodo & D. Hawksw. | BRTR10 | Parmeliaceae | |
| horsehair lichen | Bryoria trichodes (Michaux) Brodo & D. Hawksw. ssp. trichodes | BRTRT | Parmeliaceae | |
| horseradish | Armoracia rusticana P.G. Gaertn., B. Mey. & Scherb. | ARRU4 | Brassicaceae | |
| horsetail milkweed | Asclepias subverticillata (Gray) Vail | ASSU2 | Asclepiadaceae | |
| horseweed | Conyza Less. | CONYZ | Asteraceae | |
| hottentot fig | Carpobrotus edulis (L.) L. Bolus | CAED3 | Aizoaceae | |
| Houghton's flatsedge | Cyperus houghtonii Torr. | CYHO | Cyperaceae | |
| Houghton's sedge | Carex houghtoniana Torr. ex Dewey | CAHO9 | Cyperaceae | |
| hound's tongue | Cynoglossum L. | CYNOG | Boraginaceae | |
| Howell's bentgrass | Agrostis howellii Scribn. | AGHO2 | Poaceae | |
| Howell's camas | Camassia howellii S. Wats. | CAHO12 | Liliaceae | |
| Howell's mariposa lily | Calochortus howellii S. Wats. | CAHO11 | Liliaceae | |
| Howell's marsh marigold | Caltha leptosepala DC. ssp. howellii (Huth) P.G. Sm. | CALEH2 | Ranunculaceae | |
| Howell's milkvetch | Astragalus howellii Gray | ASHO3 | Fabaceae | |
| Howell's onion | Allium howellii Eastw. | ALHO2 | Liliaceae | |
| Howell's onion | Allium howellii Eastw. var. howellii | ALHOH | Liliaceae | |
| Howell's pioneer rockcress | Arabis platysperma Gray var. howellii (S. Wats.) Jepson | ARPLH2 | Brassicaceae | |
| Howell's pussytoes | Antennaria howellii Greene | ANHO | Asteraceae | |
| Howell's pussytoes | Antennaria howellii Greene ssp. howellii | ANHOH | Asteraceae | |
| Howell's pussytoes | Antennaria howellii Greene ssp. neodioica (Greene) Bayer | ANHON | Asteraceae | |
| Howell's reedgrass | Calamagrostis howellii Vasey | CAHO2 | Poaceae | |
| Huachuca Mountain dwarf mistletoe | Arceuthobium gillii Hawksworth & Wiens | ARGI2 | Viscaceae | |
| Huachuca Mountain Indian paintbrush | Castilleja patriotica Fern. | CAPA41 | Scrophulariaceae | |
| Huachuca Mountain milkvetch | Astragalus hypoxylus S. Wats. | ASHY3 | Fabaceae | |
| Huachuca Mountain sedge | Carex leucodonta Holm | CALE12 | Cyperaceae | |
| Hubricht's bluestar | Amsonia hubrichtii Woods. | AMHU | Apocynaceae | |
| Hudson Bay sedge | Carex heleonastes L. f. | CAHE4 | Cyperaceae | |
| Hudson Bay sedge | Carex heleonastes L. f. ssp. heleonastes | CAHEH2 | Cyperaceae | |
| Hudson Bay sedge | Carex heleonastes L. f. ssp. neurochlaena (Holm) Böcher | CAHEN | Cyperaceae | |
| Hudson's anemone | Anemone multifida Poir. var. hudsoniana DC. | ANMUH2 | Ranunculaceae | |
| hueso | Chionanthus axilliflorus (Griseb.) Stearn | CHAX2 | Oleaceae | |
| hueso prieto | Chionanthus holdridgei (Camp & Monachino) Stearn | CHHO4 | Oleaceae | |
| huisache daisy | Amblyolepis setigera DC. | AMSE | Asteraceae | |
| Hulten's bryhnia moss | Bryhnia hultenii Bartr. in Grout | BRHU5 | Brachytheciaceae | |
| Hulten's pitted lichen | Cavernularia hultenii Degel. | CAHU60 | Parmeliaceae | |
| Humboldt Bay owl's-clover | Castilleja ambigua Hook. & Arn. ssp. humboldtiensis (Keck) Chuang & Heckard | CAAMH | Scrophulariaceae | |
| Humboldt County milkvetch | Astragalus agnicidus Barneby | ASAG | Fabaceae | |
| Humboldt River milkvetch | Astragalus iodanthus S. Wats. | ASIO | Fabaceae | |
| Humboldt River milkvetch | Astragalus iodanthus S. Wats. var. iodanthus | ASIOI | Fabaceae | |
| Humboldt's aspicilia | Aspicilia humboldtii (Lynge) J. W. Thomson | ASHU7 | Hymeneliaceae | |
| Hungarian milkvetch | Astragalus contortuplicatus L. | ASCO17 | Fabaceae | |
| Huntsville vasevine | Clematis morefieldii Kral | CLMO6 | Ranunculaceae | |
| Hupeh cotoneaster | Cotoneaster hupehensis Rehd. & E.H. Wilson | COHU80 | Rosaceae | |
| hupilo | Coprosma menziesii Gray | COME6 | Rubiaceae | |
| hyacinth meadow garlic | Allium canadense L. var. hyacinthoides (Bush) Ownbey & Aase | ALCAH | Liliaceae | |
| hyacinth-flower clematis | Clematis heracleifolia DC. | CLHE5 | Ranunculaceae | |
| hybrid beardgrass | Bothriochloa hybrida (Gould) Gould | BOHY | Poaceae | |
| hybrid cloakfern | Astrolepis integerrima (Hook.) Benham & Windham | ASIN19 | Pteridaceae | |
| hybrid marram | ×Ammocalamagrostis baltica (Flugge ex Schrad.) P. Fourn. | AMBA8 | Poaceae | |
| 'Hycrest' | Agropyron ×hybrid auct. | AGHY2 | Poaceae | |
| hyssopleaf asphead | Aspicarpa hyssopifolia Gray | ASHY4 | Malpighiaceae | |
| hyssopleaf sandmat | Chamaesyce hyssopifolia (L.) Small | CHHY3 | Euphorbiaceae | |
| Ibapah springparsley | Cymopterus ibapensis M.E. Jones | CYIB | Apiaceae | |
| Iberian knapweed | Centaurea iberica Trev. ex Spreng. | CEIB | Asteraceae | |
| Iberian spiderflower | Cleome iberica DC. | CLIB | Capparaceae | |
| icaco coco plum | Chrysobalanus icaco L. | CHIC | Chrysobalanaceae | |
| Idaho balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. idahoensis (Sharp) Cronq. | BAHOI | Asteraceae | |
| Idaho bellflower | Campanula parryi Gray var. idahoensis McVaugh | CAPAI2 | Campanulaceae | |
| Idaho bentgrass | Agrostis idahoensis Nash | AGID | Poaceae | |
| Idaho goldthread | Coptis occidentalis (Nutt.) Torr. & Gray | COOC | Ranunculaceae | |
| Idaho hawksbeard | Crepis bakeri Greene ssp. idahoensis Babcock & Stebbins | CRBAI | Asteraceae | |
| Idaho milkvetch | Astragalus conjunctus S. Wats. | ASCO11 | Fabaceae | |
| Idaho milkvetch | Astragalus conjunctus S. Wats. var. conjunctus | ASCOC10 | Fabaceae | |
| Idaho milkvetch | Astragalus conjunctus S. Wats. var. rickardii Welsh, K. Beck & F. Caplow | ASCOR2 | Fabaceae | |
| Idaho sedge | Carex idahoa Bailey | CAID | Cyperaceae | |
| Idaho springbeauty | Claytonia lanceolata Pall. ex Pursh var. idahoensis R.J. Davis | CLLAI | Portulacaceae | |
| Igniar's dotted lichen | Bacidia igniarii (Nyl.) Oksner | BAIG | Bacidiaceae | |
| iguana hackberry | Celtis iguanaea (Jacq.) Sarg. | CEIG | Ulmaceae | |
| ilama | Annona diversifolia Saff. | ANDI11 | Annonaceae | |
| ilang-ilang | Cananga (DC.) Hook. f. & T. Thomson | CANAN | Annonaceae | |
| ilang-ilang | Cananga odorata (Lam.) Hook. f. & T. Thomson | CAOD | Annonaceae | |
| Illinois flatsedge | Cyperus grayoides Mohlenbrock | CYGR11 | Cyperaceae | |
| Illinois hawthorn | Crataegus prona Ashe | CRPR5 | Rosaceae | |
| imbricate wattle | Acacia imbricata F. Muell. | ACIM4 | Fabaceae | |
| immersed clauzadea lichen | Clauzadea immersa (Hoffm.) Hafellner & Bellem. | CLIM3 | Porpidiaceae | |
| Imshaug's disc lichen | Buellia imshaugii Hafellner | BUIM2 | Physciaceae | |
| Imshaug's witch's hair lichen | Alectoria imshaugii Brodo & D. Hawksw. | ALIM | Alectoriaceae | |
| incense cedar | Calocedrus decurrens (Torr.) Florin | CADE27 | Cupressaceae | |
| incense cedar | Calocedrus Kurz | CALOC2 | Cupressaceae | |
| incised agrimony | Agrimonia incisa Torr. & Gray | AGIN3 | Rosaceae | |
| India mustard | Brassica juncea (L.) Czern. | BRJU | Brassicaceae | |
| Indian aconite | Aconitum ferox Wallich ex Ser. | ACFE | Ranunculaceae | |
| Indian albizia | Albizia lebbekoides (DC.) Benth. | ALLE2 | Fabaceae | |
| Indian anoda | Anoda abutiloides Gray | ANAB | Malvaceae | |
| Indian bael | Aegle marmelos (L.) Corr. Serr. | AEMA3 | Rutaceae | |
| indian bark | Cinnamomum tamala (Buch.-Ham.) T. Nees & Eberm. | CITA2 | Lauraceae | |
| Indian flatsedge | Cyperus nanus Willd. | CYNA2 | Cyperaceae | |
| Indian flatsedge | Cyperus nanus Willd. var. nanus | CYNAN2 | Cyperaceae | |
| Indian flatsedge | Cyperus nanus Willd. var. subtenuis Kükenth. | CYNAS | Cyperaceae | |
| Indian frankincense | Boswellia serrata Roxb. ex Colebr. | BOSE5 | Burseraceae | |
| Indian jointvetch | Aeschynomene indica L. | AEIN | Fabaceae | |
| Indian mallow | Abutilon P. Mill. | ABUTI | Malvaceae | |
| Indian manzanita | Arctostaphylos mewukka Merriam | ARME3 | Ericaceae | |
| Indian manzanita | Arctostaphylos mewukka Merriam ssp. mewukka | ARMEM2 | Ericaceae | |
| Indian milkvetch | Astragalus australis (L.) Lam. | ASAU4 | Fabaceae | |
| Indian paintbrush | Castilleja Mutis ex L. f. | CASTI2 | Scrophulariaceae | |
| Indian parsley | Aletes Coult. & Rose | ALETE | Apiaceae | |
| Indian plaintain | Arnoglossum Raf. | ARNOG | Asteraceae | |
| Indian rattlebox | Crotalaria assamica Benth. | CRAS2 | Fabaceae | |
| Indian ricegrass | Achnatherum hymenoides (Roemer & J.A. Schultes) Barkworth | ACHY | Poaceae | |
| Indian sandburr | Cenchrus biflorus Roxb. | CEBI | Poaceae | |
| Indian shot | Canna indica L. | CAIN19 | Cannaceae | |
| Indian springparsley | Cymopterus aboriginum M.E. Jones | CYAB | Apiaceae | |
| Indian Valley brodiaea | Brodiaea coronaria (Salisb.) Engl. ssp. rosea (Greene) Niehaus | BRCOR2 | Liliaceae | |
| Indian Valley spinycape | Aristocapsa insignis (Curran) Reveal & Hardham | ARIN12 | Polygonaceae | |
| Indian walnut | Aleurites moluccana (L.) Willd. | ALMO2 | Euphorbiaceae | |
| Indian woodoats | Chasmanthium latifolium (Michx.) Yates | CHLA5 | Poaceae | |
| Indianhemp | Apocynum cannabinum L. | APCA | Apocynaceae | |
| Indian's dream | Aspidotis densa (Brack.) Lellinger | ASDE6 | Pteridaceae | |
| inflated narrow-leaf sedge | Carex grisea Wahlenb. | CAGR24 | Cyperaceae | |
| inflatedscale flatsedge | Cyperus aggregatus (Willd.) Endl. | CYAG | Cyperaceae | |
| inkberry hawthorn | Crataegus multiflora Bunge | CRMU11 | Rosaceae | |
| inland leatherfern | Acrostichum danaeifolium Langsd. & Fisch. | ACDA | Pteridaceae | |
| inland sedge | Carex interior Bailey | CAIN11 | Cyperaceae | |
| intermediate balsamroot | Balsamorhiza careyana Gray var. intermedia Cronq. | BACAI | Asteraceae | |
| intermediate cup lichen | Cladonia ecmocyna Leighton ssp. intermedia (Robbins) Ahti | CLECI | Cladoniaceae | |
| intermediate orange lichen | Caloplaca intermedia (de Lesd.) Zahlbr. | CAIN39 | Teloschistaceae | |
| intermediate suncup | Camissonia intermedia Raven | CAIN23 | Onagraceae | |
| intermediate treebine | Cissus intermedia A. Rich. | CIIN3 | Vitaceae | |
| Inyo County star-tulip | Calochortus excavatus Greene | CAEX2 | Liliaceae | |
| Inyo milkvetch | Astragalus inyoensis Sheldon | ASIN8 | Fabaceae | |
| Inyo rockcress | Arabis inyoensis Rollins | ARIN | Brassicaceae | |
| iodinebush | Allenrolfea occidentalis (S. Wats.) Kuntze | ALOC2 | Chenopodiaceae | |
| Ione manzanita | Arctostaphylos myrtifolia Parry | ARMY | Ericaceae | |
| Iowa golden saxifrage | Chrysosplenium alternifolium L. var. sibiricum Seringe ex DC. | CHALS3 | Saxifragaceae | |
| Iowa moonwort | Botrychium campestre W.H. Wagner & Farrar | BOCA5 | Ophioglossaceae | |
| ipecac | Cephaelis ipecacuanha (Brot.) Tussac | CEIP | Rubiaceae | |
| Iranian knapweed | Centaurea depressa Bieb. | CEDE10 | Asteraceae | |
| ironweed | Cyanthillium Blume | CYANT2 | Asteraceae | |
| Isely's milkvetch | Astragalus iselyi Welsh | ASIS | Fabaceae | |
| Isely's stickpea | Calliandra iselyi B.L. Turner | CAIS2 | Fabaceae | |
| island ceanothus | Ceanothus megacarpus Nutt. var. insularis (Eastw.) Munz | CEMEI2 | Rhamnaceae | |
| island cetraria lichen | Cetraria islandica (L.) Ach. | CEIS60 | Parmeliaceae | |
| island cetraria lichen | Cetraria islandica (L.) Ach. ssp. crispiformis (Rasanen) Karnefelt | CEISC | Parmeliaceae | |
| island false bindweed | Calystegia macrostegia (Greene) Brummitt | CAMA24 | Convolvulaceae | |
| island false bindweed | Calystegia macrostegia (Greene) Brummitt ssp. amplissima Brummitt | CAMAA | Convolvulaceae | |
| island false bindweed | Calystegia macrostegia (Greene) Brummitt ssp. arida (Greene) Brummitt | CAMAA2 | Convolvulaceae | |
| island false bindweed | Calystegia macrostegia (Greene) Brummitt ssp. cyclostegia (House) Brummitt | CAMAC | Convolvulaceae | |
| island false bindweed | Calystegia macrostegia (Greene) Brummitt ssp. intermedia (Abrams) Brummitt | CAMAI | Convolvulaceae | |
| island false bindweed | Calystegia macrostegia (Greene) Brummitt ssp. macrostegia | CAMAM3 | Convolvulaceae | |
| island false bindweed | Calystegia macrostegia (Greene) Brummitt ssp. tenuifolia (Abrams) Brummitt | CAMAT2 | Convolvulaceae | |
| island kihifern | Adenophorus haalilioanus (Brack.) K.A. Wilson | ADHA | Grammitidaceae | |
| island manzanita | Arctostaphylos insularis Greene ex Parry | ARIN2 | Ericaceae | |
| island marlberry | Ardisia escallonoides Schiede & Deppe ex Schlecht. & Cham. | ARES | Myrsinaceae | |
| island mountain mahogany | Cercocarpus montanus Raf. var. blancheae (Schneid.) F.L. Martin | CEMOB | Rosaceae | |
| island orange lichen | Caloplaca insularis Poelt | CAIN38 | Teloschistaceae | |
| island pea | Christia Moench | CHRIS2 | Fabaceae | |
| island puzzle | Aerva sericea Moq. | AESE | Amaranthaceae | |
| island sagebrush | Artemisia nesiotica Raven | ARNE6 | Asteraceae | |
| island sand verbena | Abronia insularis Standl. | ABIN2 | Nyctaginaceae | |
| island waxweed | Cuphea parsonsia (L.) R. Br. ex Steud. | CUPA2 | Lythraceae | |
| islandthicket threeawn | Aristida refracta Griseb. | ARRE4 | Poaceae | |
| Italian alder | Alnus cordata (Loisel.) Duby | ALCO13 | Betulaceae | |
| Italian aster | Aster amellus L. | ASAM12 | Asteraceae | |
| Italian bugloss | Anchusa azurea P. Mill. | ANAZ | Boraginaceae | |
| Italian cypress | Cupressus sempervirens L. | CUSE2 | Cupressaceae | |
| Italian hawksbeard | Crepis bursifolia L. | CRBU3 | Asteraceae | |
| Italian leather flower | Clematis viticella L. | CLVI7 | Ranunculaceae | |
| Italian lords and ladies | Arum italicum P. Mill. | ARIT | Araceae | |
| Italian plumeless thistle | Carduus pycnocephalus L. | CAPY2 | Asteraceae | |
| ivy gourd | Coccinia grandis (L.) Voigt | COGR9 | Cucurbitaceae | |
| ivyleaf maple | Acer cissifolium (Siebold & Zucc.) K.Koch | ACCI5 | Aceraceae | |
| ivyleaf thoroughwort | Chromolaena ivifolia (L.) King & H.E. Robins. | CHIV | Asteraceae | |
| Iwarancusa grass | Cymbopogon jwarancusa (Jones) Schultes | CYJW | Poaceae | |
| Jack in the bush | Chromolaena odorata (L.) King & H.E. Robins. | CHOD | Asteraceae | |
| Jack in the pulpit | Arisaema Mart. | ARISA | Araceae | |
| Jack in the pulpit | Arisaema triphyllum (L.) Schott | ARTR | Araceae | |
| Jack in the pulpit | Arisaema triphyllum (L.) Schott ssp. pusillum (Peck) Huttleston | ARTRP | Araceae | |
| Jack in the pulpit | Arisaema triphyllum (L.) Schott ssp. quinatum (Buckl.) Huttleston | ARTRQ | Araceae | |
| Jack in the pulpit | Arisaema triphyllum (L.) Schott ssp. stewardsonii (Britt.) Huttleston | ARTRS | Araceae | |
| Jack in the pulpit | Arisaema triphyllum (L.) Schott ssp. triphyllum | ARTRT3 | Araceae | |
| jackass breadnut | Clibadium erosum (Sw.) DC. | CLER | Asteraceae | |
| jackbean | Canavalia Adans. | CANAV | Fabaceae | |
| jackbean | Canavalia virosa (Roxb.) Wight & Arn. | CAVI20 | Fabaceae | |
| jackfruit | Artocarpus heterophyllus Lam. | ARHE2 | Moraceae | |
| Jack's amelasorbus | ×Amelasorbus jackii Rehd. [Amelanchier alnifolia × Sorbus scopulina] | AMJA | Rosaceae | |
| Jackson false foxglove | Agalinis filicaulis (Benth.) Pennell | AGFI | Scrophulariaceae | |
| Jackson Hole thistle | Cirsium subniveum Rydb. | CISU | Asteraceae | |
| jackswitch | Corchorus hirsutus L. | COHI3 | Tiliaceae | |
| Jacob's dotted lichen | Bacidia jacobi (Tuck.) Hasse | BAJA | Bacidiaceae | |
| Jacumba milkvetch | Astragalus douglasii (Torr. & Gray) Gray | ASDO | Fabaceae | |
| Jacumba milkvetch | Astragalus douglasii (Torr. & Gray) Gray var. douglasii | ASDOD | Fabaceae | |
| Jacumba milkvetch | Astragalus douglasii (Torr. & Gray) Gray var. perstrictus (Rydb.) Munz & McBurney | ASDOP2 | Fabaceae | |
| jade plant | Crassula ovata (P. Mill.) Druce | CROV3 | Crassulaceae | |
| Jaeger's milkvetch | Astragalus pachypus Greene var. jaegeri Munz & McBurney | ASPAJ | Fabaceae | |
| jaggery palm | Caryota urens L. | CAUR3 | Arecaceae | |
| Jakutsk snowparsley | Cnidium cnidiifolium (Turcz.) Schischkin | CNCN | Apiaceae | |
| Jamaica swamp sawgrass | Cladium mariscus (L.) Pohl ssp. jamaicense (Crantz) Kükenth. | CLMAJ | Cyperaceae | |
| Jamaican broom | Chamaecrista glandulosa (L.) Greene | CHGL6 | Fabaceae | |
| Jamaican broom | Chamaecrista glandulosa (L.) Greene var. glandulosa | CHGLG3 | Fabaceae | |
| Jamaican broom | Chamaecrista glandulosa (L.) Greene var. mirabilis (Pollard) Irwin & Barneby | CHGLM2 | Fabaceae | |
| Jamaican caper | Capparis cynophallophora L. | CACY | Capparaceae | |
| Jamaican forget-me-not | Browallia americana L. | BRAM | Solanaceae | |
| Jamaican treefern | Cyathea furfuracea Baker | CYFU | Cyatheaceae | |
| James' cryptantha | Cryptantha cinerea (Greene) Cronq. | CRCI3 | Boraginaceae | |
| James' cryptantha | Cryptantha cinerea (Greene) Cronq. var. abortiva (Greene) Cronq. | CRCIA | Boraginaceae | |
| James' cryptantha | Cryptantha cinerea (Greene) Cronq. var. arenicola Higgins & Welsh | CRCIA2 | Boraginaceae | |
| James' cryptantha | Cryptantha cinerea (Greene) Cronq. var. cinerea | CRCIC | Boraginaceae | |
| James' cryptantha | Cryptantha cinerea (Greene) Cronq. var. jamesii Cronq. | CRCIJ | Boraginaceae | |
| James' cryptantha | Cryptantha cinerea (Greene) Cronq. var. laxa (J.F. Macbr.) Higgins | CRCIL | Boraginaceae | |
| James' cryptantha | Cryptantha cinerea (Greene) Cronq. var. pustulosa (Rydb.) Higgins | CRCIP | Boraginaceae | |
| James' sedge | Carex jamesii Schwein. | CAJA2 | Cyperaceae | |
| Japanese alder | Alnus japonica (Thunb.) Steud. | ALJA8 | Betulaceae | |
| Japanese angelica tree | Aralia elata (Miq.) Seem. | AREL8 | Araliaceae | |
| Japanese arisaema | Arisaema japonicum Blume | ARJA3 | Araceae | |
| Japanese barberry | Berberis thunbergii DC. | BETH | Berberidaceae | |
| Japanese bittercress | Cardamine regeliana Miq. | CARE6 | Brassicaceae | |
| Japanese callicarpa | Callicarpa japonica Thunb. | CAJA11 | Verbenaceae | |
| Japanese cedar | Cryptomeria D. Don | CRYPT4 | Cupressaceae | |
| Japanese cedar | Cryptomeria japonica (L. f.) D. Don | CRJA3 | Cupressaceae | |
| Japanese chaff flower | Achyranthes japonica (Miq.) Nakai | ACJA | Amaranthaceae | |
| Japanese chaff flower | Achyranthes japonica (Miq.) Nakai var. hachijoensis Honda | ACJAH | Amaranthaceae | |
| Japanese chestnut | Castanea crenata Sieb. & Zucc. | CACR27 | Fagaceae | |
| Japanese cup lichen | Cladonia nipponica Asah. | CLNI4 | Cladoniaceae | |
| Japanese dodder | Cuscuta japonica Choisy | CUJA | Cuscutaceae | |
| Japanese false bindweed | Calystegia hederacea Wallich | CAHE21 | Convolvulaceae | |
| Japanese glorybower | Clerodendrum japonicum (Thunb.) Sweet | CLJA3 | Verbenaceae | |
| Japanese honewort | Cryptotaenia japonica Hassk. | CRJA7 | Apiaceae | |
| Japanese horse chestnut | Aesculus turbinata Blume | AETU | Hippocastanaceae | |
| Japanese laurel | Aucuba japonica Thunb. | AUJA | Cornaceae | |
| Japanese maple | Acer palmatum Thunb. | ACPA2 | Aceraceae | |
| Japanese sedge | Carex kobomugi Ohwi | CAKO2 | Cyperaceae | |
| Japanese thimbleweed | Anemone hupehensis (hort. ex Lem.) Lem. ex Boynton | ANHU | Ranunculaceae | |
| Japanese thimbleweed | Anemone hupehensis (hort. ex Lem.) Lem. ex Boynton var. japonica (Thunb.) Bowles & W. Stern | ANHUJ | Ranunculaceae | |
| Japanese thistle | Cirsium japonicum Fisch. ex DC. | CIJA2 | Asteraceae | |
| Java aerva | Aerva javanica (Burman f.) A. L. Juss. ex Schultes | AEJA | Amaranthaceae | |
| Java almond | Canarium indicum L. | CAIN42 | Burseraceae | |
| Javanese bishopwood | Bischofia javanica Blume | BIJA | Euphorbiaceae | |
| Javanese flatsedge | Cyperus javanicus Houtt. | CYJA | Cyperaceae | |
| Javanese glorybower | Clerodendrum speciosissimum Van Geert ex Morr. | CLSP7 | Verbenaceae | |
| Javanese treebine | Cissus nodosa Blume | CINO | Vitaceae | |
| javelin bush | Condalia ericoides (Gray) M.C. Johnston | COER5 | Rhamnaceae | |
| jelly lichen | Collema auriforme (With.) Coppins & J. R. Laundon | COAU8 | Collemataceae | |
| jelly lichen | Collema callibotrys Tuck. | COCA34 | Collemataceae | |
| jelly lichen | Collema callopismum A. Massal. | COCA35 | Collemataceae | |
| jelly lichen | Collema callopismum Massal var. rhyparodes (Nyl.) Degel. | COCAR | Collemataceae | |
| jelly lichen | Collema ceraniscum Nyl. | COCE | Collemataceae | |
| jelly lichen | Collema coccophorum Tuck. | COCO25 | Collemataceae | |
| jelly lichen | Collema crispum (Hudson) Weber ex F. H. Wigg. | COCR6 | Collemataceae | |
| jelly lichen | Collema cristatum (L.) F. H. Wigg. | COCR7 | Collemataceae | |
| jelly lichen | Collema curtisporum Degel. | COCU5 | Collemataceae | |
| jelly lichen | Collema F. H. Wigg | COLLE2 | Collemataceae | |
| jelly lichen | Collema fasciculare (L.) F. H. Wigg. | COFA4 | Collemataceae | |
| jelly lichen | Collema flaccidum (Ach.) Ach. | COFL7 | Collemataceae | |
| jelly lichen | Collema fragrans (Sm.) Ach. | COFR8 | Collemataceae | |
| jelly lichen | Collema furfuraceum (Arnold) Du Rietz | COFU3 | Collemataceae | |
| jelly lichen | Collema fuscovirens (With.) J. R. Laundon | COFU60 | Collemataceae | |
| jelly lichen | Collema glebulentum (Nyl. ex Crombie) Degel. | COGL14 | Collemataceae | |
| jelly lichen | Collema leptaleum Tuck. | COLE6 | Collemataceae | |
| jelly lichen | Collema limosum (Ach.) Ach. | COLI14 | Collemataceae | |
| jelly lichen | Collema multipartitum Sm. | COMU61 | Collemataceae | |
| jelly lichen | Collema nigrescens (Hudson) DC. | CONI8 | Collemataceae | |
| jelly lichen | Collema polycarpon Hoffm. | COPO6 | Collemataceae | |
| jelly lichen | Collema pulchellum Ach. | COPU19 | Collemataceae | |
| jelly lichen | Collema pulchellum Ach. var. leucopeplum (Tuck.) Degel. | COPUL | Collemataceae | |
| jelly lichen | Collema pulchellum Ach. var. subnigrescens (Mull. Arg.) Degel. | COPUS2 | Collemataceae | |
| jelly lichen | Collema pustulatum Ach. | COPU16 | Collemataceae | |
| jelly lichen | Collema ryssoleum (Tuck.) A. Schneider | CORY60 | Collemataceae | |
| jelly lichen | Collema subflaccidum Degel. | COSU11 | Collemataceae | |
| jelly lichen | Collema subnigrescens Degel. | COSU12 | Collemataceae | |
| jelly lichen | Collema subparvum Degel. | COSU13 | Collemataceae | |
| jelly lichen | Collema tenax (Sw.) Ach. | COTE60 | Collemataceae | |
| jelly lichen | Collema tenax (Sw.) Ach. var. ceranoides (Borrer) Degel. | COTEC3 | Collemataceae | |
| jelly lichen | Collema thamnodes Riddle | COTH | Collemataceae | |
| Jenner's cynodontium moss | Cynodontium jenneri (Schimp. in Howie) Stirt. | CYJE | Dicranaceae | |
| Jepson ceanothus | Ceanothus jepsonii Greene | CEJE | Rhamnaceae | |
| Jepson ceanothus | Ceanothus jepsonii Greene var. albiflorus J.T. Howell | CEJEA | Rhamnaceae | |
| Jepson ceanothus | Ceanothus jepsonii Greene var. jepsonii | CEJEJ2 | Rhamnaceae | |
| Jepson's brickellbush | Brickellia californica (Torr. & Gray) Gray var. jepsonii B.L. Robins. | BRCAJ | Asteraceae | |
| Jepson's milkvetch | Astragalus rattanii Gray var. jepsonianus Barneby | ASRAJ | Fabaceae | |
| Jepson's onion | Allium jepsonii (Ownbey & Aase) S. Denison & McNeal | ALJE | Liliaceae | |
| Jersey knapweed | Centaurea paniculata L. | CEPA14 | Asteraceae | |
| Jersey tea | Ceanothus herbaceus Raf. | CEHE | Rhamnaceae | |
| Jerusalem oak goosefoot | Chenopodium botrys L. | CHBO2 | Chenopodiaceae | |
| jessamine | Cestrum L. | CESTR | Solanaceae | |
| Jesup's hawthorn | Crataegus jesupii Sarg. | CRJE | Rosaceae | |
| Jesup's milkvetch | Astragalus robbinsii (Oakes) Gray var. jesupii Egglest. & Sheldon | ASROJ | Fabaceae | |
| jeweled distaff thistle | Carthamus oxyacanthus Bieb. | CAOX6 | Asteraceae | |
| jeweled hawthorn | Crataegus ravida Ashe | CRRA6 | Rosaceae | |
| jeweled onion | Allium serra McNeal & Ownbey | ALSE3 | Liliaceae | |
| jeweled thistle | Cirsium araneans Rydb. | CIAR6 | Asteraceae | |
| jicama | Calopogonium caeruleum (Benth.) Suav. | CACA42 | Fabaceae | |
| jimbrush | Ceanothus sorediatus Hook. & Arn. | CESO2 | Rhamnaceae | |
| jio | Commelina benghalensis L. | COBE2 | Commelinaceae | |
| Job's tears | Coix L. | COIX | Poaceae | |
| Job's tears | Coix lacryma-jobi L. | COLA | Poaceae | |
| John Day's pincushion | Chaenactis nevii Gray | CHNE6 | Asteraceae | |
| Johnny Reb hawthorn | Crataegus versuta Beadle | CRVE11 | Rosaceae | |
| johnny-nip | Castilleja ambigua Hook. & Arn. | CAAM32 | Scrophulariaceae | |
| johnny-nip | Castilleja ambigua Hook. & Arn. ssp. ambigua | CAAMA3 | Scrophulariaceae | |
| johnny-nip | Castilleja ambigua Hook. & Arn. ssp. insalutata (Jepson) Chuang & Heckard | CAAMI2 | Scrophulariaceae | |
| Johnston's cryptantha | Cryptantha johnstonii Higgins | CRJO | Boraginaceae | |
| Johnston's rockcress | Arabis johnstonii Munz | ARJO | Brassicaceae | |
| jointed flatsedge | Cyperus articulatus L. | CYAR4 | Cyperaceae | |
| jointed goatgrass | Aegilops cylindrica Host | AECY | Poaceae | |
| jointed sandmat | Chamaesyce articulata (Brum.) Britt. | CHAR8 | Euphorbiaceae | |
| jointtail grass | Coelorachis Brongn. | COELO | Poaceae | |
| jointvetch | Aeschynomene L. | AESCH | Fabaceae | |
| Jolon clarkia | Clarkia jolonensis Parnell | CLJO2 | Onagraceae | |
| Jones' bluestar | Amsonia jonesii Woods. | AMJO | Apocynaceae | |
| Jones' columbine | Aquilegia jonesii Parry | AQJO | Ranunculaceae | |
| Jones' columbine | Aquilegia jonesii Parry var. jonesii | AQJOJ | Ranunculaceae | |
| Jones' false cloak fern | Argyrochosma jonesii (Maxon) Windham | ARJO2 | Pteridaceae | |
| Jones' rainlily | Cooperia jonesii Cory | COJO | Liliaceae | |
| Jones' sedge | Carex jonesii Bailey | CAJO | Cyperaceae | |
| Jones spiderflower | Cleome lutea Hook. var. jonesii J.F. Macbr. | CLLUJ | Capparaceae | |
| Jones' springparsley | Cymopterus jonesii Coult. & Rose | CYJO | Apiaceae | |
| Jones' waxydogbane | Cycladenia humilis Benth. var. jonesii (Eastw.) Welsh & Atwood | CYHUJ | Apocynaceae | |
| Jonesville springbeauty | Claytonia palustris Swanson & Kelley | CLPA10 | Portulacaceae | |
| Joseph's-coat | Amaranthus tricolor L. | AMTR2 | Amaranthaceae | |
| Jost Van Dyke's Indian mallow | Bastardiopsis eggersii (E.G. Baker) Fuertes & Fryxell | BAEG6 | Malvaceae | |
| joyweed | Alternanthera Forssk. | ALTER2 | Amaranthaceae | |
| Judas-tree | Cercis siliquastrum L. | CESI9 | Fabaceae | |
| jumping cholla | Cylindropuntia fulgida (Engelm.) F.M. Knuth | CYFU10 | Cactaceae | |
| jumping cholla | Cylindropuntia fulgida (Engelm.) F.M. Knuth var. fulgida | CYFUF | Cactaceae | |
| jumping cholla | Cylindropuntia fulgida (Engelm.) F.M. Knuth var. mamillata (Schott ex Engelm.) Backeberg | CYFUM | Cactaceae | |
| jumpseed | Antenoron neofiliforme (Nakai) Hara | ANNE10 | Polygonaceae | |
| junco | Adolphia infesta (Kunth) Meisn. | ADIN | Rhamnaceae | |
| Jungermann's orange lichen | Caloplaca jungermanniae (Vahl) Th. Fr. | CAJU | Teloschistaceae | |
| juniper berry | Citharexylum caudatum L. | CICA8 | Verbenaceae | |
| juniper sedge | Carex juniperorum Catling, Reznicek & Crins | CAJU2 | Cyperaceae | |
| juniper wattle | Acacia ulicifolia (Salisb.) Court | ACUL2 | Fabaceae | |
| Juratzk's amblystegium moss | Amblystegium serpens (Hedw.) Schimp. in B.S.G. var. juratzkanum (Schimp.) Rau & Herv. | AMSEJ | Amblystegiaceae | |
| Jurupa Hills suncup | Camissonia ignota (Jepson) Raven | CAIG2 | Onagraceae | |
| jute | Corchorus aestuans L. | COAE | Tiliaceae | |
| jute | Corchorus capsularis L. | COCA38 | Tiliaceae | |
| Kaempfer's glorybower | Clerodendrum kaempferi (Jacq.) Sieb. | CLKA2 | Verbenaceae | |
| Kaffir-lily | Clivia Lindl. | CLIVI | Liliaceae | |
| Kaffir-lily | Clivia minata (Lindl.) Regel | CLMI11 | Liliaceae | |
| Kahana Valley cyrtandra | Cyrtandra crenata St. John & Storey | CYCR4 | Gesneriaceae | |
| Kahili beggarticks | Bidens forbesii Sherff ssp. kahiliensis Ganders & Nagata | BIFOK | Asteraceae | |
| Kaibab agave | Agave utahensis Engelm. var. kaibabensis (McKelvey) Breitung | AGUTK | Agavaceae | |
| Kaibab bird's beak | Cordylanthus wrightii Gray ssp. kaibabensis Chuang & Heckard | COWRK | Scrophulariaceae | |
| Kaibab Plateau Indian paintbrush | Castilleja kaibabensis N. Holmgren | CAKA6 | Scrophulariaceae | |
| Kaibab pussytoes | Antennaria rosulata Rydb. | ANRO3 | Asteraceae | |
| Kaibab sedge | Carex curatorum Stacey | CACU4 | Cyperaceae | |
| Kaibab suncup | Camissonia specuicola (Raven) Raven | CASP13 | Onagraceae | |
| Kaibab suncup | Camissonia specuicola (Raven) Raven ssp. hesperia (Raven) Raven | CASPH | Onagraceae | |
| Kaibab suncup | Camissonia specuicola (Raven) Raven ssp. specuicola | CASPS3 | Onagraceae | |
| Kaiholena cyanea | Cyanea stictophylla Rock | CYST5 | Campanulaceae | |
| Kaiparowits milkvetch | Astragalus malacoides Barneby | ASMA5 | Fabaceae | |
| Kalealaha beggarticks | Bidens micrantha Gaud. ssp. kalealaha Nagata & Ganders | BIMIK2 | Asteraceae | |
| kamanomano | Cenchrus agrimonioides Trin. | CEAG | Poaceae | |
| kamanomano | Cenchrus agrimonioides Trin. var. agrimonioides | CEAGA | Poaceae | |
| kamanomano | Cenchrus agrimonioides Trin. var. laysanensis F. Br. | CEAGL | Poaceae | |
| Kamchatica rockcress | Arabis kamchatica (Fisch. ex DC.) Ledeb. | ARKA6 | Brassicaceae | |
| Kamchatka aconite | Aconitum maximum Pallas ex DC. | ACMA4 | Ranunculaceae | |
| Kamchatka cetraria lichen | Cetraria kamczatica Savicz | CEKA60 | Parmeliaceae | |
| Kamchatka thistle | Cirsium kamtschaticum Ledeb. ex DC. | CIKA | Asteraceae | |
| Kamo'oloa cyrtandra | Cyrtandra kamooloaensis St. John | CYKA12 | Gesneriaceae | |
| kanawao | Broussaisia arguta Gaud. | BRAR6 | Hydrangeaceae | |
| Kanewsk's cup lichen | Cladonia kanewskii Oksner | CLKA3 | Cladoniaceae | |
| kangaroo vine | Cissus antarctica Venten. | CIAN3 | Vitaceae | |
| Kansas aschisma moss | Aschisma kansanum Andrews | ASKA5 | Pottiaceae | |
| Kansas hawthorn | Crataegus coccinioides Ashe | CRCO2 | Rosaceae | |
| kapoktree | Ceiba pentandra (L.) Gaertn. | CEPE2 | Bombacaceae | |
| karaka nut | Corynocarpus laevigatus J.R. & G. Forst. | COLA6 | Corynocarpaceae | |
| karanda | Carissa carandas L. [excluded] | CACA74 | Apocynaceae | |
| karroothorn | Acacia karroo Hayne | ACKA2 | Fabaceae | |
| Kashmir cypress | Cupressus cashmeriana Carriere | CUCA8 | Cupressaceae | |
| katsura tree | Cercidiphyllum japonicum Sieb. & Zucc. | CEJA2 | Cercidiphyllaceae | |
| katsura tree | Cercidiphyllum Sieb. & Zucc. | CERCI3 | Cercidiphyllaceae | |
| kau silversword | Argyroxiphium kauense (Rock & Neal) O.& I. Deg. | ARKA2 | Asteraceae | |
| Kauai beggarticks | Bidens cervicata Sherff | BICE2 | Asteraceae | |
| Kauai clermontia | Clermontia clermontioides (Gaud.) Heller | CLCL | Campanulaceae | |
| Kauai clermontia | Clermontia clermontioides (Gaud.) Heller ssp. clermontioides | CLCLC | Campanulaceae | |
| Kauai clermontia | Clermontia clermontioides (Gaud.) Heller ssp. rockiana (F. Wimmer) Lammers | CLCLR | Campanulaceae | |
| Kauai cyanea | Cyanea fissa (Mann) Hbd. | CYFI6 | Campanulaceae | |
| Kauai cyanea | Cyanea fissa (Mann) Hbd. ssp. fissa | CYFIF | Campanulaceae | |
| Kauai cyanea | Cyanea fissa (Mann) Hbd. ssp. gayana (Rock) Lammers | CYFIG | Campanulaceae | |
| Kauai flatsedge | Cyperus rockii Kükenth. | CYRO2 | Cyperaceae | |
| Kauai jackbean | Canavalia kauaiensis Sauer | CAKA3 | Fabaceae | |
| Kauai kihifern | Adenophorus epigaeus (Bishop) W.H. Wagner | ADEP | Grammitidaceae | |
| Kauai pa'iniu | Astelia waialealae Wawra | ASWA4 | Liliaceae | |
| Kauai sandmat | Chamaesyce halemanui (Sherff) Croizat & Deg. | CHHA2 | Euphorbiaceae | |
| Kauai sedge | Carex kauaiensis R.W. Krauss | CAKA2 | Cyperaceae | |
| Kauai wormwood | Artemisia kauaiensis (Skottsberg) Skottsberg | ARKA3 | Asteraceae | |
| kauila | Colubrina oppositifolia Brongn. ex Mann | COOP | Rhamnaceae | |
| Kaulfuss' lipfern | Cheilanthes kaulfussii Kunze | CHKA | Pteridaceae | |
| Kaulfuss' spleenwort | Asplenium kaulfussii Schlecht. | ASKA | Aspleniaceae | |
| kauna'oa | Cuscuta sandwichiana Choisy | CUSA2 | Cuscutaceae | |
| kauri | Agathis australis (D. Don) Steudel | AGAU4 | Araucariaceae | |
| Kaweah brodiaea | Brodiaea insignis (Jepson) Niehaus | BRIN5 | Liliaceae | |
| Kay's grama | Bouteloua kayi Warnock | BOKA | Poaceae | |
| Kealia cyanea | Cyanea recta (Wawra) Hbd. | CYRE8 | Campanulaceae | |
| Kearney's bluestar | Amsonia kearneyana Woods. | AMKE | Apocynaceae | |
| Kearney's snakewood | Condalia warnockii M.C. Johnston var. kearneyana M.C. Johnston | COWAK | Rhamnaceae | |
| Kellogg's hawthorn | Crataegus kelloggii Sarg. | CRKE2 | Rosaceae | |
| Kellogg's sedge | Carex lenticularis Michx. var. lipocarpa (Holm) L.A. Standley | CALEL3 | Cyperaceae | |
| Kelsey's cryptantha | Cryptantha kelseyana Greene | CRKE | Boraginaceae | |
| Kenai birch | Betula papyrifera Marsh. var. kenaica (W.H. Evans) A. Henry | BEPAK | Betulaceae | |
| Kenilworth ivy | Cymbalaria muralis P.G. Gaertn., B. Mey. & Scherb. | CYMU | Scrophulariaceae | |
| Kennedy's bentgrass | Agrostis tandilensis (Kuntze) Parodi | AGTA | Poaceae | |
| Kennedy's milkvetch | Astragalus lentiginosus Dougl. ex Hook. var. kennedyi (Rydb.) Barneby | ASLEK | Fabaceae | |
| Kentucky lady's slipper | Cypripedium kentuckiense C.F. Reed | CYKE2 | Orchidaceae | |
| Kentucky yellowwood | Cladrastis kentukea (Dum.-Cours.) Rudd | CLKE | Fabaceae | |
| Kenyan shower | Cassia afrofistula Brenan | CAAF2 | Fabaceae | |
| Kern brodiaea | Brodiaea terrestris Kellogg ssp. kernensis (Hoover) Niehaus | BRTEK | Liliaceae | |
| Kern Canyon clarkia | Clarkia xantiana Gray ssp. parviflora (Eastw.) H.F. Lewis & Raven | CLXAP | Onagraceae | |
| Kern County evening-primrose | Camissonia kernensis (Munz) Raven | CAKE4 | Onagraceae | |
| Kern County evening-primrose | Camissonia kernensis (Munz) Raven ssp. kernensis | CAKEK | Onagraceae | |
| Kern County milkvetch | Astragalus subvestitus (Jepson) Barneby | ASSU8 | Fabaceae | |
| Kern milkvetch | Astragalus lentiginosus Dougl. ex Hook. var. kernensis (Jepson) Barneby | ASLEK2 | Fabaceae | |
| Kern Plateau bird's-beak | Cordylanthus eremicus (Coville & Morton) Munz ssp. kernensis Chuang & Heckard | COERK | Scrophulariaceae | |
| Kern River clarkia | Clarkia exilis Lewis & Vasek | CLEX | Onagraceae | |
| Kern River evening-primrose | Camissonia integrifolia Raven | CAIN22 | Onagraceae | |
| Kern's pitted onion | Allium lacunosum S. Wats. var. kernense McNeal & Ownbey | ALLAK | Liliaceae | |
| Kerr's milkvetch | Astragalus kerrii Knight & Cully | ASKE5 | Fabaceae | |
| key lime | Citrus ×aurantiifolia (Christm.) Swingle (pro sp.) [medica × sp.] | CIAU7 | Rutaceae | |
| Key West threeawn | Aristida floridana (Chapman) Vasey | ARFL | Poaceae | |
| keystone hawthorn | Crataegus tanuphylla Sarg. | CRTA2 | Rosaceae | |
| khakiweed | Alternanthera pungens Kunth | ALPU3 | Amaranthaceae | |
| khat | Catha edulis (Vahl) Forsskal ex Endl. | CAED7 | Celastraceae | |
| Kiaerskov's lidflower | Calyptranthes kiaerskovii Krug & Urban [excluded] | CAKI | Myrtaceae | |
| kidneyshape dot lichen | Arthonia reniformis (Pers.) Ach. | ARRE13 | Arthoniaceae | |
| kidneyshape sedge | Carex reniformis (Bailey) Small | CARE17 | Cyperaceae | |
| kidneyvetch | Anthyllis L. | ANTHY | Fabaceae | |
| kihifern | Adenophorus Gaud. | ADENO3 | Grammitidaceae | |
| Kilauea Mauna cyanea | Cyanea giffardii Rock | CYGI5 | Campanulaceae | |
| killer alga | Caulerpa taxifolia (Vahl) C. Ag. | CATA5 | Caulerpaceae | |
| Kindberg's climacium moss | Climacium kindbergii (Ren. & Card.) Grout | CLKI | Climaciaceae | |
| king orchid | Broughtonia domingensis (Lindl.) Rolfe | BRDO3 | Orchidaceae | |
| Kingman's dotted lichen | Bacidia kingmanii Hasse | BAKI | Bacidiaceae | |
| King's angelica | Angelica kingii (S. Wats.) Coult. & Rose | ANKI | Apiaceae | |
| King's bird's-beak | Cordylanthus kingii S. Wats. | COKI | Scrophulariaceae | |
| King's bird's-beak | Cordylanthus kingii S. Wats. ssp. densiflorus Chuang & Heckard | COKID | Scrophulariaceae | |
| King's bird's-beak | Cordylanthus kingii S. Wats. ssp. kingii | COKIK | Scrophulariaceae | |
| King's compact sandwort | Arenaria kingii (S. Wats.) M.E. Jones ssp. compacta (Coville) Maguire | ARKIC | Caryophyllaceae | |
| King's eyelashgrass | Blepharidachne kingii (S. Wats.) Hack. | BLKI | Poaceae | |
| Kings Mountain manzanita | Arctostaphylos regismontana Eastw. | ARRE7 | Ericaceae | |
| King's plateau sandwort | Arenaria kingii (S. Wats.) M.E. Jones ssp. plateauensis Maguire | ARKIP | Caryophyllaceae | |
| King's rosy sandwort | Arenaria kingii (S. Wats.) M.E. Jones ssp. rosea Maguire | ARKIR | Caryophyllaceae | |
| King's sandwort | Arenaria kingii (S. Wats.) M.E. Jones | ARKI | Caryophyllaceae | |
| King's sandwort | Arenaria kingii (S. Wats.) M.E. Jones ssp. kingii | ARKIK | Caryophyllaceae | |
| kinnikinnick | Arctostaphylos uva-ursi (L.) Spreng. | ARUV | Ericaceae | |
| kittentail | Besseya Rydb. | BESSE | Scrophulariaceae | |
| kiwi | Actinidia chinensis Planchon | ACCH5 | Actinidiaceae | |
| Klamath arnica | Arnica spathulata Greene | ARSP4 | Asteraceae | |
| Klamath Basin milkvetch | Astragalus californicus (Gray) Greene | ASCA7 | Fabaceae | |
| Klamath manzanita | Arctostaphylos klamathensis S.W. Edwards, Keeler-Wolf & W. Knight | ARKL | Ericaceae | |
| Klamath mountain mahogany | Cercocarpus montanus Raf. var. macrourus (Rydb.) F.L. Martin | CEMOM2 | Rosaceae | |
| Klamath River rockcress | Arabis rollei Rollins | ARRO11 | Brassicaceae | |
| Klamath rockcress | Arabis subpinnatifida S. Wats. | ARSU | Brassicaceae | |
| Kleberg's saltbush | Atriplex klebergorum M.C. Johnston | ATKL | Chenopodiaceae | |
| Klinggraeff's bryum moss | Bryum klinggraeffii Schimp. in Klinggr. | BRKL2 | Bryaceae | |
| Klotzsch's brachymenium moss | Brachymenium klotzschii (Schwaegr.) Par. | BRKL | Bryaceae | |
| Knapp brickellbush | Brickellia knappiana E. Drew | BRKN | Asteraceae | |
| knapweed | Centaurea L. | CENTA | Asteraceae | |
| knapweed | Cyanopsis Cass. | CYANO | Asteraceae | |
| kneeling angelica | Angelica genuflexa Nutt. | ANGE2 | Apiaceae | |
| Knieskern's hawthorn | Crataegus knieskerniana Sarg. | CRKN | Rosaceae | |
| knife acacia | Acacia cultriformis A. Cunn. ex G. Don | ACCU4 | Fabaceae | |
| knifeleaf condalia | Condalia spathulata Gray | COSP3 | Rhamnaceae | |
| Knight's milkvetch | Astragalus knightii Barneby | ASKN | Fabaceae | |
| knight's-spur | Consolida S.F. Gray | CONSO | Ranunculaceae | |
| knob sedge | Carex inversa R. Br. | CAIN49 | Cyperaceae | |
| knobcone pine dwarf mistletoe | Arceuthobium siskiyouense Hawksworth, Wiens & Nickrent | ARSI10 | Viscaceae | |
| knobthorn | Acacia nigrescens Oliv. | ACNI8 | Fabaceae | |
| knotsheath sedge | Carex retrorsa Schwein. | CARE4 | Cyperaceae | |
| knotweed spineflower | Chorizanthe polygonoides Torr. & Gray | CHPO4 | Polygonaceae | |
| knotweed spineflower | Chorizanthe polygonoides Torr. & Gray var. longispina (Goodman) Munz | CHPOL | Polygonaceae | |
| knotweed spineflower | Chorizanthe polygonoides Torr. & Gray var. polygonoides | CHPOP5 | Polygonaceae | |
| Knowlton's bryum moss | Bryum knowltonii Barnes | BRKN2 | Bryaceae | |
| Knudsen's birdnest fern | Asplenium polyodon G. Forst. var. knudsenii (Hbd.) Morton | ASPOK | Aspleniaceae | |
| koa | Acacia koa Gray | ACKO | Fabaceae | |
| koaoha | Acacia koaia Hbd. | ACKO2 | Fabaceae | |
| Koehler's rockcress | Arabis koehleri T.J. Howell | ARKO | Brassicaceae | |
| Koehler's rockcress | Arabis koehleri T.J. Howell var. koehleri | ARKOK | Brassicaceae | |
| Koehler's rockcress | Arabis koehleri T.J. Howell var. stipitata Rollins | ARKOS | Brassicaceae | |
| Kohala Mountain clermontia | Clermontia drepanomorpha Rock | CLDR2 | Campanulaceae | |
| Kohala Mountain cyrtandra | Cyrtandra kohalae Rock | CYKO | Gesneriaceae | |
| kohlrabi | Brassica oleracea L. var. gongylodes L. | BROLG2 | Brassicaceae | |
| koi | Coprosma kauensis (Gray) Heller | COKA | Rubiaceae | |
| koko | Chamaesyce atrococca (Heller) Croizat & Deg. | CHAT2 | Euphorbiaceae | |
| kokolau | Bidens amplectens Sherff | BIAM3 | Asteraceae | |
| kokomalei | Chamaesyce kuwaleana (O. Deg. & Sherff) O.& I. Deg. | CHKU | Euphorbiaceae | |
| kolekole cyanea | Cyanea kolekoleensis (St. John) Lammers | CYKO3 | Campanulaceae | |
| Koloa clermontia | Clermontia ?carinifera Levl. | CLCA6 | Campanulaceae | |
| Konocti manzanita | Arctostaphylos manzanita Parry ssp. elegans (Eastw.) P.V. Wells | ARMAE | Ericaceae | |
| Koolau Range beggarticks | Bidens asymmetrica (Levl.) Sherff | BIAS3 | Asteraceae | |
| Koolau Range cyrtandra | Cyrtandra kalihii Wawra | CYKA5 | Gesneriaceae | |
| Koolau Range papala | Charpentiera ovata Gaud. | CHOV2 | Amaranthaceae | |
| Koolau Range papala | Charpentiera ovata Gaud. var. niuensis Sohmer | CHOVN | Amaranthaceae | |
| Koolau Range papala | Charpentiera ovata Gaud. var. ovata | CHOVO | Amaranthaceae | |
| Koolau Range rollandia | Cyanea crispa (Gaud.) Lammers, Givnish & Sytsma | CYCR9 | Campanulaceae | |
| Koolau Range sandmat | Chamaesyce rockii (Forbes) Croizat & Deg. | CHRO2 | Euphorbiaceae | |
| ko'oloa 'ula | Abutilon menziesii Seem. | ABME2 | Malvaceae | |
| kou | Cordia subcordata Lam. | COSU2 | Boraginaceae | |
| Kousa dogwood | Cornus kousa Hance | COKO2 | Cornaceae | |
| Krause's sedge | Carex krausei Boeckl. | CAKR2 | Cyperaceae | |
| Kremmling milkvetch | Astragalus osterhoutii M.E. Jones | ASOS | Fabaceae | |
| kuawawaenohu | Alsinidendron lychnoides (Hbd.) Sherff | ALLY3 | Caryophyllaceae | |
| Kunth's cyanea | Cyanea kunthiana (Gaud.) Hbd. | CYKU | Campanulaceae | |
| Kunth's onion | Allium kunthii G. Don | ALKU | Liliaceae | |
| kwahu | Barleria opaca (Vahl) Nees | BAOP3 | Acanthaceae |
Source: U. S. Department of Agriculture
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