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Pictured: Alnus viridis — the species. This subspecies isn’t separately illustrated.
Betulaceae family

Mountain Alder (subsp. crispa) Alnus viridis subsp. crispa subspecies

Native
Deer-resistant — Low palatability to browsing deer. Usually passed over, but no plant is truly deer-proof when food is scarce.

Mountain Alder (subsp. crispa) is a perennial tree native to Canada, Greenland, and the lower 48 states. It grows to 10 ft and blooms Jul in full sun – part shade, with brown fruit. A keystone plant for native insects and the food web.

More about this plant

Alnus alnobetula, the green alder, is a common shrub or small tree widespread across much of Europe, Asia, and North America. Many sources refer to it as Alnus viridis but this is a later name, synonymous with Alnus alnobetula subsp. alnobetula. The species was first described by Jakob Friedrich Ehrhart in 1783 as Betula alnobetula, while the name viridis was first used later, as Betula viridis, in 1785. Wikipedia →

Growing & care

USDA PLANTS · TRY
Conditions
Sources · Conditions
USDA PLANTS — Sun · Soil & moisture
USDA — SoilPH — Soil pH
USDA PLANTS (DwCA, Zenodo 17903503) — Fertility Requirement / Soil Adaptation — Fertility need · Adapts to
USDA — Temp-Min °F — Hardiness
Sun
Full sun – part shade
Soil & moisture
High moisture
Soil pH
4.8–7
Fertility need
Medium
Adapts to
Coarse (sandy), Medium (loam)
Hardiness
USDA zone 1+
Size & form
Sources · Size & form
USDA PLANTS (DwCA, Zenodo 17903503) — Height, Mature — Height
USDA PLANTS (DwCA, Zenodo 17903503) — Planting Density (per acre) — Spacing
USDA PLANTS (DwCA, Zenodo 17903503) — Growth Rate / Spread / Growth Form / Lifespan / Active Growth Period / Seed Period — Spread · Growth rate · Growth form · Active growth
USDA PLANTS — Lifespan
USDA PLANTS — FoliageTexture — Foliage
USDA PLANTS (DwCA, Zenodo 17903503) — Fruit/Seed Color / Fruit Persistence — Fruit
Lifespan: USDA’s lifespan scale for trees: short = under ~100 years · moderate = 100–250 · long = over 250. Balsam fir and other short-lived conifers are genuinely short for a tree, not short like an annual.
Height
10 ft
Spacing
5–8 ft apart from USDA planting density
Spread
Slow
Growth rate
Moderate
Growth form
Thicket-forming
Lifespan
Perennial · moderate
Foliage
medium texture
Active growth
Spring & summer
Fruit
Brown
In the garden
Sources · In the garden
USDA PLANTS (DwCA, Zenodo 17903503) — Propagation Method / Commercial Availability — Propagate by · In the trade
USDA PLANTS (DwCA, Zenodo 17903503) — Germination (cold stratification) — Seed starting
USDA PLANTS — Seed Period — Seeds ripen
USDA PLANTS (DwCA, Zenodo 17903503) — Foliage Texture / Browse Palatability / Resprout — Deer browsing · Resprouts if cut
Propagate by
Seed, 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
Shrub layer — Sits in the shrub of a layered food forest or polyculture.Open guide →
derived roles
The garden year bloom → fruit → fall colour
J
F
M
A
M
J
J
A
S
O
N
D
Bloom
Bloom (the flower's colour)
Bloom · Jul — USDA PLANTS (DwCA, Zenodo 17903503) — BloomPeriod
When to sow · for your area

Sow timing keys off your local last- and first-frost dates.

Species characteristics from USDA PLANTS (public domain) + TRY (CC BY) — general guidance, not a guarantee for your exact site. Deer "browsing" is documented palatability, not a deer-proof claim.

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:

Abagrotis variata · owlet moth Acerra normalis · owlet moth Achatia distincta · Distinct Quaker Achatodes zeae · Elder Shoot Borer Acleris braunana · leafroller moth Acleris caliginosana · leafroller moth
+ 8 more species →
Acleris cervinana · leafroller moth Acleris cornana · leafroller moth Acleris fuscana · Small Aspen Leaftier Acleris hudsoniana · leafroller moth Acleris inana · Inane Acleris Acleris logiana · leafroller moth Acleris maccana · leafroller moth Acleris semiannula · leafroller moth
Keystone count (genus-level) from Warren II 2026 (CC0) · Tallamy host-use records. Named species (a documented Nearctic sample, not exhaustive) from NHM HOSTS (CC0).
Species thumbnails re-hosted from iNaturalist — Creative Commons, credited per image (hover for credit). Click any species to see it on iNaturalist. Not exhaustive; many taxa have no openly-licensed photo yet.
Sources for this entry (24) Open & cited
[01] Scientific name & family — USDA PLANTS (DwCA, Zenodo 17903503)
[02] Growth habit & duration — USDA PLANTS (DwCA, Zenodo 17903503)
[03] Native status & distribution — USDA PLANTS (DwCA, Zenodo 17903503)
[04] Common name — USDA PLANTS (via GBIF)
[18] Invasive / introduced status — USDA PLANTS (DwCA, Zenodo 17903503) — native status
[19] Description — Wikipedia (CC BY-SA)
[20] Ecological value — Warren II 2026 (CC0) · Tallamy host-use counts
[21] Conservation rank — NatureServe Explorer (CC BY)
[22] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[23] Caterpillar species — NHM HOSTS (CC0)
Spot an error or have a better photo? Every field links to its source, and the whole dataset is open.
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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