Description
The showy and beautiful red-flowered Western thistle (Cirsium occidentale) is found on poor soil with good drainage with harsh sun, in open grassland, chaparral or rocky areas with very little surrounding competition from other plants. It is a biennial plant that forms a rosette the first year, flowering the second year before producing seed and dying out. In drought years or on particularly harsh sites it may take multiple years to flower. When in flower the height of the plant may vary from 1′-6′ tall.
Western thistle has many additional common names, including snowy thistle, cobweb thistle, or cobwebby thistle. There are also many varieties of the species. The common names are due to the appearance of the spines of the flowers which are laced in fibers resembling cobwebs or snow.
Western thistle is native to California, Oregon and Nevada. Despite their eye-catching beauty and value for pollinators and birds, native thistle species have long been undervalued. Native thistles are never aggressive and won’t spread rapidly like their non-native and invasive relatives.
Thistles are in the sunflower family (Asteraceae), with many individual flowers packed within each flower head, protected by a spiny involucre. Like a sunflower, each flower produces a single seed, and each seed head produces many seeds.
Nutritious thistle seeds are highly prized by birds such as the Lesser or American goldfinch. According to the Oregon Department of Fish and Wildlife, “Their diet is composed almost entirely of seeds, with those of the sunflower family, particularly thistles, strongly preferred.” Birds also use the fluffy thistle chaff to line their nests.
The list of butterfly species that use native thistles for nectar is too numerous to list here. It is common to see butterflies nectaring on native thistles in the wild. Several butterfly species use native thistles as a larval host plant, including: Painted lady (Vanessa cardui), Mylitta crescent (Phyciodes mylitta), and the California crescent (Phyciodes orseis). Hummingbirds are especially fond of thistle nectar. Often spending a considerable amount of time around a thistle patch, sipping nectar in between aerial acrobatics. Additionally, native bees and pollinating flies and beetles also forage on and pollinate native thistles.
Western thistle is deer resistant and drought tolerant.
Western thistle (Cirsium occidentale) seed packets contain approximately 40 seeds per packet.
Seed Germination Instructions
No pretreatement required for fresh seed. Germination may be improved with 30 days cold-moist stratification. Sow outside in early fall to late winter. Seeds may germinate with early fall rain if sown in early fall. Seed stored for a year or more may need 60-90 days cold-moist stratification for germination.
For detailed information about growing Western thistle, please see our Growing Native Thistles guide.
