European alder
Alnus glutinosa · Betulaceae
European alder (Alnus glutinosa) is a perennial tree in the Betulaceae family. It is introduced to North America rather than native. USDA records it as hardy in zone 5 and warmer, down to about -18°F.
⚠ Invasive or noxious status. USDA lists this plant with an invasive or noxious weed status somewhere in its range. Check your state's noxious weed list before planting it — in some states it is illegal to sell or plant.
Both flags are quoted from USDA PLANTS, not inferred.
At a glance
| Type | tree USDA |
|---|---|
| Lifecycle | perennial USDA |
| Native status | introduced USDA |
| Mature height | 45 ft USDA |
| Light | part-shade USDA |
| Water need | medium USDA |
| Growth rate | rapid USDA |
| Soil pH | 4.4–7.2 USDA |
| Bloom | April–May USDA |
| Flower color | Purple USDA |
| Hardiness zones | 5 and warmer USDA |
| Guild layer | canopy 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 moderate water needs. Its drought tolerance is rated medium. It is recorded on soils from pH 4.4 to 7.2 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 5.
Size and growth
At maturity it reaches about 45 ft, making it a substantial woody plant. It grows quickly.
Bloom period
USDA records a bloom period of April through May. Flowers are purple.
A flowering date, not a pollinator rating.
Foliage, flower and season
Summer foliage is green, medium in texture. Its flowers are not conspicuous — a plant for form and foliage. Its fruit or seed heads are conspicuous, extending interest past flowering. Its active growth period is spring and summer. USDA rates its lifespan as moderate.
What the site needs to provide
USDA records it across sites receiving 20 to 65 inches of annual precipitation. It needs at least 130 frost-free days to finish its season. It roots to at least 16 inches. Fertility requirement: low — no feeding needed on ordinary garden soil.
Propagating it
It takes readily from seed, cuttings, 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 does not spread vegetatively, so it will stay where you put it.
Resilience and wildlife
Browsing animals rate it barely palatable — the sourced basis for calling it deer-resistant. Its fire tolerance is rated low, and it can resprout after damage. Its growth form is recorded as multiple stem.
Role in a guild
Canopy. In a layered planting this is the tallest layer of a planting — it sets the light budget everything beneath it lives on. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Others in Alnus
- gray alder Alnus incana
- speckled alder Alnus incana
- thinleaf alder Alnus incana
- seaside alder Alnus maritima
Similar role and hardiness
- tree of heaven Ailanthus altissima
- water hickory Carya aquatica
- southern catalpa Catalpa bignonioides
- Chinese chestnut Castanea mollissima
- American holly Ilex opaca
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol ALGL2, 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 color, flower conspicuous, foliage color, foliage porosity winter, foliage texture, frost free days min, fruit conspicuous, growth form, Growth rate, Hardiness zones, Invasive status, 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, Type, vegetative spread rate, Water need.
- Derived by a fixed rule from those columns: Guild layer.
Read our full data sources and methodology.
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