Aquatic Milkweed Asclepias perennis
Aquatic Milkweed is a perennial wildflower native to the lower 48 states. It blooms May – Aug. Monarch host plant.
More about this plant
Asclepias perennis, also known as aquatic milkweed or white swamp milkweed, is a North American species of milkweed that is found throughout the Coastal Plain from eastern Texas to southern South Carolina, northward along the Mississippi River, and into the Ohio Valley of Illinois, Indiana, and Kentucky. There seems to be a few disjunct populations in Arkansas, Texas, and Indiana. Wikipedia →
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 7 derived from its U.S. range
- Lifespan
- Perennial
- Flower colour
- Pink AI AI image-analysis of community-science photos — lower-confidence (a more subjective call, often an inconspicuous flower); 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, Aquatic 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 2 bee visitors
2 native & managed bee species are documented visiting Aquatic Milkweed :
Wildlife & visitors 21 nectaring
Open records of who else uses Aquatic Milkweed — a generalist food-web signal, kept separate from the keystone Ecological Value.
21 adult butterfly & moth species are recorded nectaring at its flowers — the most-recorded:
Across 27 U.S. vegetation-survey plots that recorded Aquatic Milkweed, these catalog species turned up most often in the same plot — a real field co-occurrence signal, not a planting prescription.
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 (21) 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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