Rush Milkweed Asclepias subulata
Rush Milkweed is a perennial shrub native to the lower 48 states. It grows to 2.6 ft and blooms Jan – Dec. Monarch host plant.
More about this plant
Asclepias subulata is a species of milkweed known commonly as the rush milkweed, desert milkweed or ajamete. This is an erect perennial herb which loses its leaves early in the season and stands as a cluster of naked stalks. Atop the stems are inflorescences of distinctive flowers. Each cream-white flower has a reflexed corolla that reveals the inner parts, a network of five shiny columns, each topped with a tiny hook. The fruit is a pouchlike follicle that contains many flat, oval seeds with long, silky hairlike plumes. This milkweed is native to the desert southwest of the United States and northern Mexico. It grows in dry slopes, mesas, plains and desert washes. Wikipedia →
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 10 derived from its U.S. range
- Height
- 2.6 ft
- Lifespan
- Perennial
- Foliage
- Broadleaf
- Flower colour
- Yellow AI AI image-analysis of community-science photos (~87% expert agreement) — not a botanical record
Wildlife & pollinators
How pollinator value is scored →★ Monarch Larval host plant
A monarch host plant.
Monarch caterpillars eat only milkweeds (Asclepias). As a native milkweed, Rush Milkweed is a documented larval host across its breeding range.
❧ Caterpillar hosts ~12 caterpillar species
Asclepias supports ~12 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 moderate genus.
Recorded feeding on Asclepias in North America, including:
+ 8 more species → ↑ show fewer
✦ Bees 16 bee visitors
16 native & managed bee species are documented visiting Rush Milkweed — the 12 most-recorded:
Wildlife & visitors 17 nectaring
Open records of who else uses Rush Milkweed — a generalist food-web signal, kept separate from the keystone Ecological Value.
17 adult butterfly & moth species are recorded nectaring at its flowers — the most-recorded:
Related plants
More Asclepias →
How we know this (2) Methods & honest limits
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.
McKenzie et al. assigned each species a flower colour with a GPT-4V vision model over iNaturalist photos. We use the confident tier plus a separately-labelled lower-confidence top-up (mostly inconspicuous green/brown flowers), and render it as a small tint — never as an asserted fact, and kept out of the written synopsis.
Honest limits: AI image inference (~87% expert agreement on the confident tier); a decorative, confidence-tiered indicator, not a measured trait.
Sources for this entry (24) 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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