Sand Dune Thistle Cirsium pitcheri
Sand Dune Thistle is a biennial wildflower native to Canada and the lower 48 states. A host for pollen-specialist native bees.
More about this plant
Cirsium pitcheri, sometimes called Pitcher's thistle or dune thistle, is a species of thistle native to sand dune shorelines along the upper Great Lakes. It is native to Indiana, Illinois, Michigan, Wisconsin, and Ontario. It is listed by the U.S. Fish and Wildlife Service as a threatened species. Wikipedia →
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 6 derived from its U.S. range
- Lifespan
- Biennial
- Flower colour
- Purple AI AI image-analysis of community-science photos (~87% expert agreement) — not a botanical record
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~29 caterpillar species
Cirsium supports ~29 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 Cirsium in North America, including:
+ 8 more species → ↑ show fewer
✦ Bees specialist-bee host · 6 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. Cirsium is a recorded specialist-bee host, so losing it can mean losing the bee that relies on it.
6 native & managed bee species are documented visiting Sand Dune Thistle :
Related plants
More Cirsium →
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 (19) 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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