Bull Thistle
Bull thistle flowerheads are comprised of hundreds of smaller flowers. Photo credit: WNY PRISM
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Common Name: Bull Thistle
Scientific Name: Cirsium vulgare
Origin: Africa, Asia and Europe
Description
Bull thistle is an herbaceous biennial that grows up to six feet tall. During its first year of growth, bull thistle produces a basal rosette of deeply lobed, hairy leaves that have a sharp spine at the end of each lobe. During its second year, it sends up a single, occasionally branched, stem that produces multiple purple to pink flowerheads with a diameter of 1.5-2 inches. A single flowerhead is comprised of hundreds of smaller flowers that develop into plume-topped seeds.
Habitat
Bull thistle prefers moderate moisture and disturbed sites such as forest clear cuts, pastures, and along roads or fences.
Threat
Bull thistle forms dense stands that outcompete native species. This reduces diversity and forage availability for both livestock and wildlife.
Management
Manual removal is effective for small populations and can be done by either removing the whole plant or cutting its taproot prior to it setting seed. Chemical control is effective as well and can be done in the early spring or late fall. Mechanical removal is also useful when paired with other control strategies but should not be used for long-term control.
Regional Distribution
Widespread
WNY PRISM Priority
Tier 4 – Local Control
Invasive Species Priorities – Tier Chart
Pathways
Bull thistle was likely first introduced in the early 1800s, via contaminated seed. It reproduces exclusively by seed with each flowerhead producing up to 300 seeds. The seeds can travel long distances by wind and remain viable for up to ten years.
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