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Alnus (incana)

John Vandevender
Center Manager
USDA NRCS - Appalachian Plant Materials Center
P. O. Box 390
Alderson, West Virginia 24910

Family Scientific Name: Betulaceae
Family Common Name: Birch
Scientific Name: Alnus incana (L.) Moench rugosa (Du Roi) R.T. Clausen
Common Name: speckled alder
Species Code: ALINR
Ecotype: Canaan Valley Wildlife Refuge
Known Invasiveness: None
Propagation Goal: plants
Propagation Method: seed
ProductType: Bareroot (field grown)
Stock Type: Bareroot
Time To Grow: 1 Years
Target Specifications: A second spring seedling ranging in height from 6" to 12" with a 1/16" to 1/8" caliper stem and a compact, well developed root system.
Propagule Collection: Speckled alder is a monoecious plant. Flowering occurs in the spring before leaf emergence. Seed is produced in pistillate ovoid strobiles or conelets (cones). Pollen is contributed from staminate catkins which are formed the preceding autumn and occur in small clusters. The catkins are naked and erect during the winter and become much elongated and pendulous at maturity. Pistillate aments are also erect and naked during the winter and occur in short racemes or elongated panicles. Aments enlarge slightly at flowering and develop into ovate strobiles or conelets upon pollination. Smooth alder fruit (seed) is a small, compressed, slightly winged nutlet borne in pairs at the base of each cone scale. Fruit matures in autumn. Ripe cones are thick, somewhat woody and dark brown in color. Compared to other alder species, smooth alder is more densely branched and produces more fruit. Smooth alder produces fruit (seed) every year and a good seed crop every four years. Seed typically matures in late autumn (October and November). Cones with mature seed should be harvested promptly and stored in paper bags at room temperature only until the cones dry.
Propagule Processing: Seeds are released as the cones dry. Cones may be shaken and/or crushed by hand or mechanically to extract the seed. Seed may be separated from the crushed cones by hand or a mechanical seed cleaner using combinations of #14, 9, 6, and 1/18 screens.
Pre-Planting Treatments: Speckled alder seed does not maintain its germination in storage. Seed should be sown in nursery beds within one month of harvest.
Growing Area Preparation/
Annual Practices for Perennial Crops:
Best germination and growth of seedlings is in raised beds or sandy soil with adequate moisture. Prepare beds by deep rototilling or other tillage methods that achieve thorough loosening and mixing of soil. Nursery beds must be inoculated with soil from an alder stand to provide the nitrogen fixing bacteria necessary for adequate growth. Seed can be broadcast over the bed and lightly covered with sand or soil or sown in 1/4 inch deep rows and covered lightly. Recommended seeding rates are 50 grams of seed broadcast per 100 square feet of bed or 15 grams of seed per 10 linear feet of row. Beds should be covered with a 2 - 3 inch thick layer of straw to insulate against frost heaving. When seedlings begin to emerge, one-half of the straw should be removed.
Establishment Phase: Germination occurs in the spring after an overwinter period of cool, moist natural stratification.
Length of Establishment Phase: 4-6 months, including natural stratification period
Active Growth Phase: Plants require little maintenance during active growth other than application of at least 1 inch of water per week during drouth conditions and elimination of weed competition. Weeds must be removed during early growth phases to avoid uprooting the alder seedlings.
Length of Active Growth Phase: 6-8 months
Hardening Phase: Since the plants are grown outside, no additional hardening is required.
Length of Hardening Phase: None
Harvesting, Storage and Shipping: Seedlings are harvested in late winter while dormant. The best harvesting method employs a nursery bed lifter/shaker which undercuts the seedlings and gently loosens the soil around the roots. Bare root seedlings are then plucked from the loosened soil by hand. Refrigeration is employed to maintain seedling dormancy after harvest until shipping. Optimal temperatures for maintenance of dormancy are 35-40 degrees Fahrenheit. Root dessication during storage is prevented through packing in aged, moistened hardwood sawdust.
Length of Storage: 1-2 months
Other Comments: Speckled alder is resistant to most disease and insect pests. It is browsed by deer and domestic livestock and is very palatable to beaver. Seed orchards should be protected by fencing to prevent damage from deer and beaver.
References: van Dersal, William R. 1938. Native Woody Plants of the United States: Their Erosion Control and Wildlife Values. US Government Printing Office, Washington, DC

Thunhorst, Gwendolyn A. 1993. Wetland Planting Guide for the Northeastern US. Environmental Concern, St. Michaels, MD

Mylona, Panagiota, Katharina Pawloski and Tom Bisseling. 1995. Symbiotic Nitrogen Fixation. The Plant Cell, Vol. 7, pp. 869-885

Harrington, Constance A., Leslie Chandler Brodie, Dean S. DeBell, and C. S. Schopmeyer. 1979. Alnus P. Mill. published in Symbiotic Nitrogen Fixation in the Management of Temperate Forests. Gordon, J. C., C. T. Wheller and D. A. Perry, eds.

Strausbaugh, P. D. and E. L. Core. 1977. Flora of West Virginia, 2nd Edition

USDA, NRCS. 2008. The PLANTS Database (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

USDA, Forest Service. 1948. Woody-Plant Seed Manual, Misc. Pub. No. 654, US Government Printing Office, Washington, DC.


Vandevender, John. 2008. Propagation protocol for production of Bareroot (field grown) Alnus incana (L.) Moench plants Bareroot; USDA NRCS - Appalachian Plant Materials Center Alderson, West Virginia. In: Native Plant Network. URL: http://NativePlantNetwork.org (accessed 2020/09/18). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.

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