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iNaturalist — CC, credited & licensed per image
Betulaceae family

Arizona Alder Alnus oblongifolia

Native
Early-season nectar — Flowers in a late-winter / early-spring window when few other plants in our catalog bloom — valuable early forage for pollinators (relative to our catalog's bloom coverage).
Also known as: Mexican alder · New Mexican alder

Arizona Alder is a perennial tree native to the lower 48 states. It grows to 33 ft and blooms Feb – Sep. A keystone plant for native insects and the food web.

More about this plant

Alnus oblongifolia is a large alder growing up to 72 feet (22 m), from the southwestern United States and northern Sonora, Mexico. It grows across Arizona into western New Mexico mountain ranges. In central Arizona its range extends across the transition zone to the White Mountains region of eastern Arizona–western New Mexico border. 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 8 derived from its U.S. range
Drought tolerance
Low
Shade tolerance
Low
Wet-soil tolerance
Moderate waterlogging
Size & form
Sources · Size & form
TRY Plant Trait Database (CC BY 4.0) — Height · Foliage
USDA PLANTS — Lifespan
Height
33 ft
Lifespan
Perennial
Foliage
Deciduous broadleaf
In the garden
Sub-canopy / understory layer — Sits in the understory of a layered food forest or polyculture.Open guide →
Rain garden / bioswale — Rated FACW on the wetland list — tolerates wet feet, so it suits the soggy zone of a rain garden or bioswale that catches and filters runoff.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 · Feb – Sep — 35 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:

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.
How we know this (2) 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).
Climate niche (heat tolerance & native rainfall) Derived

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.

Realized-niche / climate-envelope approach (Pearson & Dawson 2003; Soberón 2007). Climate: NOAA NCEI nClimDiv county normals (1991–2020).
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 (23) 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)
[14] Functional traits — TRY Plant Trait Database (CC BY 4.0)
[15] Photosynthetic pathway — TRY Plant Trait Database (CC BY 4.0)
[16] Climate niche — Derived — realized climate niche from U.S. county occurrences (GBIF) × NOAA NCEI county climate normals 1991–2020 (public domain)
[17] Cold hardiness (derived) — Derived from U.S. range × USDA PHZM zones
[19] Other common names — Wikidata (CC0)
[20] Stress tolerance — Niinemets & Valladares 2006 (CC0)
[21] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[22] Caterpillar species — NHM HOSTS (CC0)
[23] County range — GBIF Open Data — open-licensed occurrences (CC0/CC-BY) → county
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