European Alder Alnus glutinosa
European Alder is an introduced perennial tree, found in Canada and the lower 48 states. It grows to 45 ft and blooms Apr in full sun – part shade, with brown fruit.
More about this plant
Alnus glutinosa, the common alder, black alder, European alder, European black alder, or just alder, is a species of tree in the family Betulaceae, native to most of Europe, southwest Asia and northern Africa. It thrives in wet locations where its association with the bacterium Frankia alni enables it to grow in poor quality soils. It is a medium-sized, short-lived tree growing to a height of up to 30 metres (98 feet). It has short-stalked rounded leaves and separate male and female flowers in the form of catkins. The small, rounded fruits are cone-like and the seeds are dispersed by wind and water. Wikipedia →
European Alder is flagged invasive in the U.S. These natives fill a similar niche — same growth habit, bloom season, height, and region — so you keep the look and feed local wildlife instead of spreading a problem.
Growing & care
USDA PLANTS · TRY- Sun
- Full sun – part shade
- Soil & moisture
- Medium moisture
- Soil pH
- 4.4–7.2
- Fertility need
- Low
- Adapts to
- Coarse (sandy), Medium (loam), Fine (clay)
- Hardiness
- USDA zone 6+
- Drought tolerance
- Low
- Shade tolerance
- Moderate
- Wet-soil tolerance
- High waterlogging
- Height
- 45 ft
- Mature width
- ≈ 30 ft wide wild/forest-grown — open-grown specimens spread wider
- Spacing
- 6–17 ft apart from USDA planting density
- Spread
- None — clumping
- Growth rate
- Rapid
- Growth form
- Multiple stems
- Lifespan
- Perennial · moderate
- Foliage
- Deciduous broadleaf · medium texture
- Active growth
- Spring & summer
- Fruit
- Brown persists into winter
- Propagate by
- Seed, Cuttings, Bare root, Container
- Seed starting
- Needs cold stratification a cold-moist spell before it germinates
- Seeds ripen
- Summer – Autumn seed-collection / harvest window
- In the trade
- Routinely available
- Deer browsing
- Low often deer-resistant
- Resprouts if cut
- Yes regrows after top-kill
Sow timing keys off your local last- and first-frost dates.
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~255 caterpillar species · keystone genus
Alnus supports ~255 caterpillar species.
Native butterfly & moth caterpillars are the base of the terrestrial food web — most songbirds rear their young almost entirely on them. As a host for native Lepidoptera this is a powerhouse genus.
Recorded feeding on Alnus in North America, including:
+ 8 more species → ↑ show fewer
✦ Bees 6 bee visitors
6 native & managed bee species are documented visiting European Alder :
Wildlife & visitors 6 birds · 1 mammal · 4 nectaring
Open records of who else uses European Alder — a generalist food-web signal, kept separate from the keystone Ecological Value.
Recorded eaten by 6 birds and 1 mammal species (fruit, seed, browse):
+ 1 more species → ↑ show fewer
4 adult butterfly & moth species are recorded nectaring at its flowers:
Related plants
More Alnus →
How we know this (3) Methods & honest limits
We read each species’ measured specific leaf area (leaf area per unit dry weight) from the Global Spectrum dataset and band it: thin & fast (high SLA), medium, or thick & tough (low SLA). The global median is about 10 mm²/mg.
Honest limits: A species-mean from pooled measurements — individual plants vary with light and site. A broad strategy signal, not a precise per-plant figure.
A recorded categorical fact: each species is tagged C3 (standard), C4 (heat/water-efficient) or CAM (succulent, night-time CO₂ uptake) — or a facultative combination. We only show a trait card for the noteworthy C4/CAM cases; C3 is the unremarkable majority, kept in the data but not surfaced as a card.
We take the plant’s U.S. county range and look up each county’s long-term climate, then summarise: native rainfall = the median annual rainfall across its counties; heat tolerance = the warm end (90th percentile) of average temperature across its range (mirroring how our cold-hardiness floor uses an extreme). Counties + medians blunt the roadside/observer bias that makes point-level climate unreliable. Needs at least five placeable counties.
Honest limits: A realized, sampling-biased niche (where it has been recorded, not its physiological optimum), and county climate is coarse — large Western counties span deserts and mountains. Derived guide, never a measured fact.
Sources for this entry (38) Open & cited
Cite this page Open data, please attribute
PlantKey’s data is open under CC BY-SA 4.0 — free to reuse and adapt, with attribution and the same licence. Photos keep their own per-image licence + credit (see Sources above).
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