Purpleosier Willow Salix purpurea
Purpleosier Willow is an introduced perennial tree, found in Canada and the lower 48 states. It grows to 9 ft and blooms Apr – May.
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 5 derived from its U.S. range
- Drought tolerance
- Low
- Shade tolerance
- Low
- Wet-soil tolerance
- High waterlogging
- Height
- 9 ft
- Lifespan
- Perennial
- Foliage
- Deciduous broadleaf
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~455 caterpillar species · keystone genus
Salix supports ~455 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 Salix in North America, including:
+ 8 more species → ↑ show fewer
✦ Bees specialist-bee host · 28 bee visitors
Specialist native bees depend on it.
Some native bees are pollen specialists (oligolectic) — they raise young only on pollen from particular plant genera. Salix is a recorded specialist-bee host, so losing it can mean losing the bee that relies on it.
28 native & managed bee species are documented visiting Purpleosier Willow — the 12 most-recorded:
Wildlife & visitors 57 birds · 4 mammals · 6 nectaring
Open records of who else uses Purpleosier Willow — a generalist food-web signal, kept separate from the keystone Ecological Value.
Recorded eaten by 57 birds and 4 mammals species (fruit, seed, browse) — the most-recorded:
+ 4 more species → ↑ show fewer
6 adult butterfly & moth species are recorded nectaring at its flowers:
Related plants
More Salix →
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 (28) 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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