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Betulaceae family

Green Alder Alnus viridis

Native

Green Alder is a perennial tree native to Alaska, Canada, and Greenland. It blooms May – Aug. 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
Cold hardiness (derived) — Hardiness
Niinemets & Valladares 2006 (CC0) — Drought tolerance · Shade tolerance · Wet-soil tolerance
Hardiness
≥ zone 5 derived from its U.S. range
Drought tolerance
Low
Shade tolerance
Low
Wet-soil tolerance
Moderate waterlogging
Size & form
Sources · Size & form
USDA PLANTS — Lifespan
TRY Plant Trait Database (CC BY 4.0) — Foliage
Lifespan
Perennial
Foliage
Deciduous broadleaf
In the garden
Tree layer (canopy / understory) — Sits in the tree 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 · May – Aug — 80 obs · Herbarium specimens — Park et al. 2023 (CC BY 4.0)
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:

Acronicta lanceolaria · Pointed Dagger Moth ✦ Anagoga occiduaria · geometer (inchworm) moth ✦ Apotomis bifida · leafroller moth ✦ Aseptis binotata · owlet moth ✦ Caloptilia alnivorella · leaf-blotch miner moth ✦ Clepsis melaleucana · Black-Patched Clepsis Moth ✦
+ 8 more species →
Clepsis persicana · White Triangle Tortrix ✦ Coleophora persimplexella · casebearer moth ✦ Cyclophora pendulinaria · Sweetfern Geometer ✦ Eupithecia sheppardata · geometer (inchworm) moth ✦ Hyalophora euryalus · Ceanothus Silkmoth ✦ Iridopsis emasculata · geometer (inchworm) moth ✦ Itame exauspicata · geometer (inchworm) moth ✦ Lithophane petulca · owlet 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). ✦ = recorded on this exact species.
Wildlife & visitors 5 mammals

Open records of who else uses Green Alder — a generalist food-web signal, kept separate from the keystone Ecological Value.

Interaction records (observations, not exhaustive) from GloBI → (CC0). Counts are distinct species; names are the most-recorded. Common names from Wikidata (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.
How we know this (1) Methods & honest limits
Photosynthesis Direct fact

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.

Kattge, J. et al. TRY plant trait database — Categorical Traits Dataset (2012).
Derived values are computed from open data by a published method — labelled, cited, and never shown as a direct observation. Full methodology →
Sources for this entry (18) 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)
[05] Invasive / introduced status — USDA PLANTS (DwCA, Zenodo 17903503) — native status
[06] Wetland indicator — USACE National Wetland Plant List (2022)
[08] Description — Wikipedia (CC BY-SA)
[09] Ecological value — Warren II 2026 (CC0) · Tallamy host-use counts
[11] Conservation rank — NatureServe Explorer (CC BY)
[13] Photosynthetic pathway — TRY Plant Trait Database (CC BY 4.0)
[14] Cold hardiness (derived) — Derived from U.S. range × USDA PHZM zones
[15] Wildlife & visitors — GloBI — Global Biotic Interactions (CC0)
[16] Stress tolerance — Niinemets & Valladares 2006 (CC0)
[17] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[18] 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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