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Anderson, Wynn

Alnus incana

Alnus incana (L.) Moench

Gray Alder, Mountain Alder, Speckled Alder, River Alder, Thin-leafed Alder

Betulaceae (Birch Family)

Synonym(s):

USDA Symbol: alin2

USDA Native Status: L48 (N), AK (N), CAN (N), SPM (N)

Speckled alder is a tall shrub or small tree, typically 20-40 ft. tall, but the western form, Alnus incana ssp. tenuifolia may reach 80 feet in height with multiple, crooked, leggy trunks. Bent in a wide curve at their base, the trunks become upright and picturesque. Deciduous leaves are rounded and coarsely toothed, remaining dark-green in autumn. The flower is a purplish-red catkin and the fruit is a woody cone.

This is the common alder throughout the Rocky mountains and wet areas westward nearing the Pacific Ocean.

From the Image Gallery

7 photo(s) available in the Image Gallery

Plant Characteristics

Duration: Perennial
Habit: Shrub , Tree
Leaf Retention: Deciduous
Leaf Arrangement: Alternate
Leaf Complexity: Simple
Leaf Shape: Elliptic , Ovate
Leaf Venation: Pinnate
Leaf Margin: Double-serrate
Leaf Apex: Acuminate , Acute , Obtuse
Leaf Base: Cuneate , Rounded
Breeding System: Flowers Unisexual , Monoecious
Fruit Type: Samara
Size Notes: Height: 6-12(-25)meters. The eastern subspecies, Alnus incana ssp. rugosa, grows as a large shrub and may reach 9 meters in height. The larger form, A. i. ssp. tenuifolia, is found west of the Rocky Mountains in the US and Canada and grows as a large shrub or tree and typically tops out around 12 meters, but can reach 25 meters in height.
Leaf: Green

Bloom Information

Bloom Color: Red , Green
Bloom Time: Mar , Apr , May

Distribution

USA: AK , AZ , CA , CO , CT , IA , ID , IL , IN , MA , MD , ME , MI , MN , MT , ND , NH , NJ , NM , NV , NY , OH , OR , PA , RI , UT , VA , VT , WA , WI , WV , WY
Canada: AB , BC , MB , NB , NL , NS , ON , PE , QC , SK
Native Distribution: Lab. to AK, s. to NJ, mts. of WV, n.e. IL, n.e. IA, MN, n.e. ND & w. mts. to NM & c. CA
Native Habitat: Wetlands & stream edges

Growing Conditions

Water Use: High
Light Requirement: Sun , Part Shade , Shade
Soil Moisture: Moist , Wet
Soil pH: Circumneutral (pH 6.8-7.2)
CaCO3 Tolerance: Low
Soil Description: Wet soils.
Conditions Comments: Alnus rugosa and Alnus tenuifolia are now classified as subspecies of Alnus incana. Fast-growing and flood tolerant, this species is short-lived, rarely exceeding 40 years. It can be thicket-forming and provides erosion control along watercourses in the mountains. Alders bear nitrogen-fixing root nodules and thus serve as nutrient-giving pioneers in reclamation projects.

Benefit

Use Wildlife: Songbirds, waterbirds, and mammals frequently use this species.
Use Other: The Navajo Indians made a red dye from the powdered bark.
Interesting Foliage: yes

Propagation

Description: Seeds of most alders germinate when they are fresh without pretreatment.
Seed Treatment: If seeds have dried in storage, a cool-moist stratification at 41 degrees for 180 days will be necessary.
Commercially Avail: yes

Find Seed or Plants

View propagation protocol from Native Plants Network.

Mr. Smarty Plants says

Alder native to Central Indiana
May 30, 2006
I am trying to find out whether there exists a plant named Alnus rugosa. I bought a plant recently that said Speckled Alder, Alnus serrulata (rugosa), but have been unable to determine if this is a c...
view the full question and answer

National Wetland Indicator Status

Region:	AGCP	AK	AW	CB	EMP	GP	HI	MW	NCNE	WMVE
Status:	FACU	FAC	FACW		FACU	FACW		FACW	FACW	FACW

This information is derived from the U.S. Army Corps of Engineers National Wetland Plant List, Version 3.1 (Lichvar, R.W. 2013. The National Wetland Plant List: 2013 wetland ratings. Phytoneuron 2013-49: 1-241). Click here for map of regions.

From the National Organizations Directory

According to the species list provided by Affiliate Organizations, this plant is on display at the following locations:

Natural Biodiversity - Johnstown, PA

Additional resources

USDA: Find Alnus incana in USDA Plants
FNA: Find Alnus incana in the Flora of North America (if available)
Google: Search Google for Alnus incana

Metadata

Record Modified: 2021-03-30
Research By: TWC Staff

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