gray alder
Alnus incana · Betulaceae
gray alder (Alnus incana) is a perennial tree in the Betulaceae family. It is native to North America. USDA records it as hardy in zone 3 and warmer, down to about -33°F.
At a glance
| Type | tree Derived |
|---|---|
| Lifecycle | perennial USDA |
| Native status | native USDA |
| Mature height | 25 ft USDA |
| Light | part-shade USDA |
| Water need | high USDA |
| Growth rate | rapid USDA |
| Soil pH | 5–7 USDA |
| Bloom | March–May USDA |
| Hardiness zones | 3 and warmer USDA |
| Guild layer | understory Derived |
| Nursery availability | Routinely Available USDA |
USDA quoted from the USDA PLANTS database · Derived computed by a fixed rule from those columns. No value on this page is estimated.
Growing conditions
It grows in partial shade. USDA rates it as having needs consistently moist ground. Its drought tolerance is rated low. It tolerates saturated, poorly drained ground well (USDA rates its anaerobic tolerance high). It is recorded on soils from pH 5 to 7 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 3.
Size and growth
At maturity it reaches about 25 ft, making it a substantial woody plant. It grows quickly.
Bloom period
USDA records a bloom period of March through May.
A flowering date, not a pollinator rating.
Foliage, flower and season
Summer foliage is green, coarse in texture. Its flowers are not conspicuous — a plant for form and foliage. Its active growth period is spring and summer. USDA rates its lifespan as short, so plan on replacing or resowing it rather than treating it as permanent structure.
What the site needs to provide
USDA records it across sites receiving 32 to 60 inches of annual precipitation. It needs at least 100 frost-free days to finish its season. It roots to at least 24 inches. Fertility requirement: medium.
Propagating it
Propagate it from seed, bare root and container stock. Seed needs cold stratification — a period of moist chilling — before it will germinate, so sow in autumn or chill it artificially before a spring sowing. Its seed spreads at a slow rate. It spreads vegetatively at a slow rate.
Resilience and wildlife
Browsing animals find it moderately palatable, so expect deer and rabbits to take an interest. Its fire tolerance is rated high. Its growth form is recorded as thicket forming.
Role in a guild
Understory. In a layered planting this is the layer beneath the canopy, tall enough to hold structure but shaded from above. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Others in Alnus
- European alder Alnus glutinosa
- speckled alder Alnus incana
- thinleaf alder Alnus incana
- seaside alder Alnus maritima
Similar role and hardiness
- bigtooth maple Acer grandidentatum
- Canadian serviceberry Amelanchier canadensis
- gray birch Betula populifolia
- American hornbeam Carpinus caroliniana
- cockspur hawthorn Crataegus crus-galli
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol ALIN2, or is computed from those values by a fixed rule. Nothing here is estimated or model-generated. Where USDA publishes no value, this page omits the claim rather than filling the gap.
- Quoted from USDA PLANTS: active growth period, Bloom, Bloom end, browse palatability, cold stratification, Drought tolerance, fall conspicuous, fertility requirement, fire tolerance, flower conspicuous, foliage color, foliage porosity winter, foliage texture, frost free days min, fruit conspicuous, growth form, Growth rate, Hardiness zones, Lifecycle, lifespan, Light, Mature height, Minimum temperature, Native status, Nitrogen fixation, Nursery availability, precipitation max in, precipitation min in, propagation, resprout ability, root depth in, seed spread rate, Soil pH, Soil pH (upper), Tolerance of wet soil, Toxicity, vegetative spread rate, Water need.
- Derived by a fixed rule from those columns: Guild layer, Type.
Read our full data sources and methodology.
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