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iNaturalist — CC, credited & licensed per image
Pictured: Cirsium undulatum — the species. This variety isn’t separately illustrated.
Asteraceae family

Tracy's Thistle (var. tracyi) Cirsium undulatum var. tracyi variety

Native Specialist-bee host

Tracy's Thistle (var. tracyi) is a biennial wildflower native to the lower 48 states. A host for pollen-specialist native bees.

More about this plant

Cirsium undulatum is a species of thistle known by the common names wavyleaf thistle and gray thistle. It is native to much of central and western North America from British Columbia east to Manitoba and south as far as the State of Durango in Mexico. It has also been found outside of its native range as an introduced species. Wikipedia →

Growing & care

USDA PLANTS · TRY
Conditions
Sources · Conditions
Cold hardiness (derived) — Hardiness
Hardiness
≥ zone 7 derived from its U.S. range
Size & form
Sources · Size & form
USDA PLANTS — Lifespan
Lifespan
Biennial
In the garden
Herb layer — Sits in the herb of a layered food forest or polyculture.Open guide →
derived roles
Species characteristics from USDA PLANTS (public domain) + TRY (CC BY) — general guidance, not a guarantee for your exact site. Deer "browsing" is documented palatability, not a deer-proof claim.

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:

Anagrapha falcifera · Celery Looper Autographa precationis · Common Looper Calephelis mutica · Swamp Metalmark Calephelis virginiensis · Little Metalmark Cnephasia longana · leafroller moth Dicymolomia julianalis · Julia's Dicymolomia
+ 8 more species →
Endopiza viteana · leafroller moth Euxoa auxiliaris · Army Cutworm Moth Hedya cyanana · leafroller moth Homoeosoma ammonastes · snout moth Homoeosoma ardaloniphas · snout moth Homoeosoma electella · Sunflower Moth Homoeosoma eremophasma · snout moth Homoeosoma impressale · snout moth
Keystone count (genus-level) from Warren II 2026 (CC0) · Tallamy host-use records. Named species (a documented Nearctic sample, not exhaustive) from NHM HOSTS (CC0).
✦ Bees specialist-bee host

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.

Xerces pollinator conservation →
Specialist hosts from Smith et al. 2024.
Species thumbnails re-hosted from iNaturalist — Creative Commons, credited per image (hover for credit). Click any species to see it on iNaturalist. Not exhaustive; many taxa have no openly-licensed photo yet.
Sources for this entry (13) Open & cited
[01] Scientific name & family — USDA PLANTS (DwCA, Zenodo 17903503)
[02] Growth habit & duration — USDA PLANTS (DwCA, Zenodo 17903503)
[03] Native status & distribution — USDA PLANTS (DwCA, Zenodo 17903503)
[04] Common name — USDA PLANTS (via GBIF)
[05] Invasive / introduced status — USDA PLANTS (DwCA, Zenodo 17903503) — native status
[06] Description — Wikipedia (CC BY-SA)
[07] Ecological value — Warren II 2026 (CC0) · Tallamy host-use counts · Smith et al. 2024 (CC BY)
[08] Conservation rank — NatureServe Explorer (CC BY)
[09] Cold hardiness (derived) — Derived from U.S. range × USDA PHZM zones
[11] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[12] Caterpillar species — NHM HOSTS (CC0)
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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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