Plant Guide

Alnus incana (L.) Moench
gray alder
ALIN2

Summary
Duration	Perennial
Growth Habit	Tree, Shrub
U.S. Nativity	Native to U.S.
Federal T/E Status
National Wetland Indicator	FACU, FACW

Morphology/Physiology
Active Growth Period	Spring and Summer
After Harvest Regrowth Rate
Bloat
C:N Ratio	High
Coppice Potential	No
Fall Conspicuous	No
Fire Resistant	No
Flower Color
Flower Conspicuous	No
Foliage Color	Green
Foliage Porosity Summer	Moderate
Foliage Porosity Winter	Porous
Foliage Texture	Coarse
Fruit/Seed Color	Brown
Fruit/Seed Conspicuous	No
Growth Form	Thicket Forming
Growth Rate	Rapid
Height at 20 Years, Maximum (feet)	15
Height, Mature (feet)	25
Known Allelopath	No
Leaf Retention	No
Lifespan	Short
Low Growing Grass	No
Nitrogen Fixation	Medium
Resprout Ability	No
Shape and Orientation	Erect
Toxicity	None

Growth Requirements
Adapted to Coarse Textured Soils	Yes
Adapted to Fine Textured Soils	Yes
Adapted to Medium Textured Soils	Yes
Anaerobic Tolerance	High
CaCO3 Tolerance	Low
Cold Stratification Required	Yes
Drought Tolerance	Low
Fertility Requirement	Medium
Fire Tolerance	High
Frost Free Days, Minimum	100
Hedge Tolerance	None
Moisture Use	High
pH, Minimum	5
pH, Maximum	7
Planting Density per Acre, Minimum	300
Planting Density per Acre, Maximum	1200
Precipitation, Minimum	32
Precipitation, Maximum	60
Root Depth, Minimum (inches)	24
Salinity Tolerance	None
Shade Tolerance	Intermediate
Temperature, Minimum (°F)	-33

Reproduction
Bloom Period	Spring
Commercial Availability	Routinely Available
Fruit/Seed Abundance	Low
Fruit/Seed Period Begin	Spring
Fruit/Seed Period End	Summer
Fruit/Seed Persistence	No
Propagated by Bare Root	Yes
Propagated by Bulb	No
Propagated by Container	Yes
Propagated by Corm	No
Propagated by Cuttings	No
Propagated by Seed	Yes
Propagated by Sod	No
Propagated by Sprigs	No
Propagated by Tubers	No
Seed per Pound	1084250
Seed Spread Rate	Slow
Seedling Vigor	Low
Small Grain	No
Vegetative Spread Rate	Slow

Suitability/Use
Berry/Nut/Seed Product	No
Christmas Tree Product	No
Fodder Product	No
Fuelwood Product	Medium
Lumber Product	No
Naval Store Product	No
Nursery Stock Product	No
Palatable Browse Animal	Medium
Palatable Graze Animal	Low
Palatable Human	No
Post Product	No
Protein Potential	Low
Pulpwood Product	No
Veneer Product	No

Kingdom Plantae -- Plants

Subkingdom Tracheobionta -- Vascular plants

Superdivision Spermatophyta -- Seed plants

Division Magnoliophyta -- Flowering plants

Class Magnoliopsida -- Dicotyledons

Subclass Hamamelididae

Order Fagales

Family Betulaceae -- Birch family

Genus Alnus P. Mill. -- alder P

Species Alnus incana (L.) Moench -- gray alder P

Alternate Names

Thin-leafed alder, grey alder, mountain alder, river alder

Uses

Ethnobotanic: Native Americans reportedly pounded the wood of thin leaf alder into a powder to produce a red dye (Lanner 1983). The wood was occasionally used for firewood. It is also valued by cabinetmakers and is used in making clogs, bowls, and woodcuts.

Wildlife: Cottontails, muskrats, moose, elk, deer, and snowshoe hares eat the leaves and twigs. Redpolls, siskins, chickadees, and goldfinches eat alder seeds, buds, and catkins. Beavers eat the bark and build dams with the stems.

Agroforestry: Alnus incana is an excellent pioneer species for revegatating disturbed riparian areas or as a mass planting to achieve a screen or windbreak. Thin-leaf alder is used in tree strips for windbreaks, which are planted and managed to protect livestock, enhance production, and control soil erosion. Windbreaks can help communities with harsh winter conditions better handle the impact of winter storms and reduce home heating costs during the winter months.

Status

Please consult the Plants Web site and your State Department of Natural Resources for this plant’s current status, such as, state noxious status and wetland indicator values.

Description

General: Thin-leafed alder is a native, deciduous shrub or tree. The leaves are ovate, double serrated, and pointed at the tip. Male catkins are produced in the autumn in-groups of three or four. The female catkins are borne separately on the same plant in late winter or early spring. The fruit are small, brown, scale-like cones produced in early autumn. The bark is thin, smooth, and green-gray, grayish-brown, or reddish-brown (Preston 1948).

Distribution: Thin-leaf alder is distributed throughout Europe and much of North America. For current distribution, please consult the Plant profile page for this species on the PLANTS Web site.

Adaptation

This shrub or small tree tolerates a wide range of soil types. It grows best in heavy moist soils in light shaded areas. It has a high flood tolerance and typically grows near rivers and moist stream borders on poorly developed soil. Thin-leaf alder is frequently found growing in the understory of coniferous forests on moist sites. It is also adaptable to a range of soil pH levels.

Establishment

Propagation from Seed: Seed is best sown as soon as it is ripe in a cold frame. If Alnus incana seeds are not sown in the fall, they require cold stratification for three months before germination. Sow the seeds in containers or seed trays containing a slow release fertilizer. Firm the medium and place the seeds thinly and evenly on top. When large enough to handle, the seeds can be placed into individual pots. If growth is sufficient, they may be planted into their permanent positions in the summer, if not they can be planted in the spring.

Management

Thin-leaf alder often occurs in dense thickets, which reportedly results from underground rhizomes or suckers (Dayton 1931). If plants are damaged, sprouting can occur from the stump, root collar, or from the root crown following fire. After top-removal of plants by beavers, they have been observed to sprout heavily from the cut.

Propagation from cuttings is not recommended and plants are not widely available in nurseries.

Cultivars, Improved and Selected Materials (and area of origin)

Somewhat available through native plant nurseries within it range.

References

Arno, S.F. 1977. Northwest trees. The Mountaineers, Seattle, Washington.

Coombes, A.J. 1992. Eyewitness handbooks: trees. Dorling Kindersley, Inc., New York, New York.

Davis, Brian. 1987. The gardener’s illustrated encyclopedia of trees and shrubs. Rodale Press, Inc., Emmaus, Pennsylvania.

Dayton, W.A. 1931. Important western browse plants. Misc. Publication 101. Washington, D.C.

Dirr, M.A. 1990. Manual of woody landscape plants: their identification, ornamental characteristics, culture, propagation, and uses. 4^th ed. Stipes Publishing Company, Champaign, Illinois.

Dirr, M.A. & C.W. Heuser 1987. The reference manual of woody plant propagation: from seed to tissue culture. Varsity Press, Athens, Georgia.

Epple, A.O. 1995. A field guide to the plants of Arizona. Falcon Press, Helena, Montana.

Haeussler, S & D. Coates 1986. Autecological characteristics of selected species that compete in British Columbia: a literature review. Land Management Report No. 33. Victoria, BC.

Heuser, C.W. 1997. The complete book of plant propagation. The Taunton Press, Newtown, Connecticut.

Lanner, R.M. 1983. Trees of the Great Basin: a natural history. University of Nevada Press, Reno, Nevada.

Martin, A.C.; H.S. Zim & A.L. Nelson 1951. American wildlife and plants. McGraw-Hill Book Company, Inc., New York, New York.

McMinn, H.E. 1939. An illustrated manual of California shrubs. University of California Press, Berkeley, Los Angeles, & London.

Nelson, R.A. 1992. Handbook of Rocky Mountain plants. Roberts Rinehart Publishers, Newot, Colorado.

Preston, R.J., Jr. 1948. North American trees. The Iowa State College Press, Ames, Iowa.

U.S. Department of Agriculture, Forest Service. 1937. Range plant handbook. Washington, DC.

Prepared By

Jammie Favorite

Formerly USDA, NRCS, National Plant Data Center

Baton Rouge, Louisiana

Species Coordinator

M. Kat Anderson

USDA, NRCS, National Plant Data Center, c/o Plant Science Dept., Davis, California

Edited: 29jan03 jsp; 09jun03 ahv; 30may06jsp

For more information about this and other plants, please contact your local NRCS field office or Conservation District, and visit the PLANTS Web site<https://plants.usda.gov> or the Plant Materials Program Web site <https://Plant-Materials.nrcs.usda.gov>

Attribution: U.S. Department of Agriculture