SelecTree

A Tree Selection Guide

MOUNTAIN ALDER

Alnus incana subsp. tenuifolia

FAMILY Betulaceae

SYNONYMS

Alnus tenuifolia

ADDITIONAL COMMON NAMES

THIN-LEAF ALDER

SPECKLED ALDER

WESTERN RIVER ALDER

THINLEAF ALDER

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See: all Alnus
Photo locations: Morton Arboretum - Lisle, IL, UC Berkeley Botanic Garden - Berkeley, CA, Los Angeles County Arboretum - Arcadia, CA and Regional Parks Botanic Garden, Tilden Regional Park - Berkeley, CA
by C. Stubler, J. Reimer, M. Ritter

GENERAL INFO

Extremely hardy to cold. The name incana refers to the white underside of the leaves. Often found near water.
Native range: CaliforniaHorticultural use: Riparian or Screen

TREE CHARACTERISTICS

Tree Shape: RoundedFoliage Type: DeciduousMaximum Tree Height: 25 feetCanopy Width: 15-20 feetGrowth Rate: ~24-36 in/yearLeaf Arrangement and Leaf Form: Alternate, SimpleLeaf Shape: OvateLeaf color: GreenFall Color: YesFlowers: InconspicuousFlower Color: Green or Red or YellowFlower Type: Has male and female reproductive parts in each flower (perfect)Flower Time: SpringFruit: Medium Brown ConeFruiting time: Fall, Winter or SummerBark Color: Dark Gray or Red Brown, SmoothLitter Type: Dry Fruit

SITE CONDITIONS

Recommended Planting Area: 4' to 7'Water Use Rating: HighSunset Climate Zone: 2 - 3, 7, 10Shade Tolerance: NoUSDA Hardiness Zone: 5, 6, 7, 8Soil Texture: Loam or SandSoil pH: Very Acidic to NeutralSalt Tolerance: Low

CONSIDERATIONS

Root Damage Potential: ModeratePotential health issues: AllergyWildlife interactions: Attracts birdsDisease and Pest susceptibility: Armillaria, Root Rot, Powdery MildewUtility Friendly: NoWCISA Appraisal: Suggested LCANT 24" box, Group —, Approx. cross sectional area —

External Resources

WikipediaiNaturalistKew

CITE THIS TREE

"SelecTree. UFEI. "Alnus incana subsp. tenuifolia Tree Record." 1995-2025. Cal Poly State University, San Luis Obispo. Accessed on May 9, 2025."
< https://selectree.calpoly.edu/tree-detail/155 >

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