photo: Forest & Kim Starr, Starr Environmental, Bugwood.org
Bull Thistle (Cirsium vulgare)
 Forest & Kim Starr, Starr Environmental, Bugwood.org |
 Steve Dewey, Utah State University, Bugwood.org |
 Dan Tenaglia, Missouriplants.com, Bugwood.org |
 Steve Dewey, Utah State University, Bugwood.org |
 Michael Shephard, USDA Forest Service, Bugwood.org |
Form:
Biennial thistles grow vegetatively the first year after germination, forming a basal rosette 4-18" wide. Plants produce one to several flowering stalks (bolt) in subsequent years (typically 2nd). Bull thistle bolts 2-3 weeks later than the other thistles, which usually begin in Late May. Ranges from 1-5' tall.
Leaves:
Opposite, 4 to 6 inches across, 5-7 lobes, juice milky, few large teeth.
Flowers:
Purple flowers bloom spring - early fall. Bull thistle flowers 2-3 weeks after other thistles. Flowers are 1-2" wide, gumdrop shape, and each bract is tipped with long, stiff spine.
Fruits & Seeds:
Small seeds (about 0.12") inside of a thin-walled fruit (achene). Loosely attached to feathery tuft of hair.
Roots:
Taproot.
Tier 3 - Presence is of Interest
The species that occur in this tier are likely ornamental escapes. It is not known whether they are established and/or spreading within Cleveland Metroparks. The ecological impact is poorly known for these species.
Action: The presence of these plants should be recorded by approximating the number of plants. Initial population numbers are likely small.
