Rocky Mountain Maple Acer glabrum
Rocky Mountain Maple is a perennial tree native to Canada and the lower 48 states. It grows to 30 ft and blooms May in full sun – part shade, with brown fruit. A keystone plant for native insects and the food web.
More about this plant
Acer glabrum is a species of maple native to western North America, from southeastern Alaska, British Columbia and western Alberta, east to western Nebraska, and south through Washington, Oregon, Idaho, Montana and Colorado to California, Arizona, Utah, and New Mexico. Wikipedia →
Growing & care
USDA PLANTS · TRY- Sun
- Full sun – part shade
- Soil & moisture
- Low moisture
- Soil pH
- 5.8–7.5
- Fertility need
- Medium
- Adapts to
- Coarse (sandy), Medium (loam)
- Hardiness
- USDA zone 3+
- Drought tolerance
- Moderate
- Shade tolerance
- Moderate
- Wet-soil tolerance
- Low waterlogging
- Height
- 30 ft
- Mature width
- ~ 25 ft wide DERIVED derived estimate — open-grown crown allometry (height × growth-form ratio); not a measurement
- Spacing
- 6–12 ft apart from USDA planting density
- Spread
- Moderate
- Growth rate
- Rapid
- Growth form
- Multiple stems
- Lifespan
- Perennial · moderate
- Foliage
- Deciduous broadleaf · coarse texture
- Active growth
- Spring & summer
- Fruit
- Brown
- 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
- Medium moderately palatable
- 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 ~297 caterpillar species · keystone genus
Acer supports ~297 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 Acer in North America, including:
+ 8 more species → ↑ show fewer
Wildlife & visitors 1 bird · 1 nectaring
Open records of who else uses Rocky Mountain Maple — a generalist food-web signal, kept separate from the keystone Ecological Value.
Recorded eaten by 1 bird species (fruit, seed, browse):
1 adult butterfly & moth species is recorded nectaring at its flowers:
Across 291 U.S. vegetation-survey plots that recorded Rocky Mountain Maple, these catalog species turned up most often in the same plot — a real field co-occurrence signal, not a planting prescription.
Related plants
More Acer →
How we know this (4) 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.
For woody plants that have a height but no measured crown, we estimate width = height × a crown-to-height ratio fit for that plant’s form (conifers narrower than broadleaf trees, shrubs widest), calibrated on our measured open-grown crowns and capped at the largest one ever measured. A measured crown always wins; herbaceous plants get nothing (no anchor).
Honest limits: A coarse class-median estimate for garden-scale spacing, not a measurement; woody single/multi-stem forms only.
Sources for this entry (36) 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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