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Pest Information

Bull Thistle

Bull Thistle

  • Latin Name: Cirsium Vulgare
  • Common Name: Bull Thistle
  • Other Names: Common thistle, common bull thistle, spear thistle

Pest Details

Bull Thistle
Bull Thistle
Bull Thistle

Origin:

Native to Europe and Asia, but now widespread throughout the United States and southern Canada.

Biology:

A biennial weed that is a problem in virtually any setting – landscape, crops, roadsides, ditchbanks, etc. The basal rosette of leaves germinates in late fall and remains green through the winter. The stems and flower heads are produced the second summer and will remain as dead remnants through the following winter.

Identification:

Mature plants are as high as 5 feet tall, with the flower stalks at least half of that height. There is a single main stem with simple branching at its base, and with extensive branching at the upper length. The stems have furrows running their length and they are covered with wooly hairs. The leaves have clasping wings at their base and are alternate along the stem. Lower leaves may be 12 inches long, have a short stalk, and are deeply lobed. Leaves are covered with coarse hairs on both surfaces, as well as having stiff spines on the tips of the lobes. Flower heads occur in clusters of 4 or 5 at the tops of the stems, being produced from late spring into the fall. Each flower head is at the end of its own long stalk. Below the flowers there is a large ball of spiny bracts, and flowers are purple to reddish, or sometimes white. The seeds that form are tipped with many long, whitish hairs (pappus) that enable them to be wind-borne.

Characteristicts Important to Control:

Heavy seed production and seed dispersal by the wind allow easy spread of this weed. Physical removal is easy with skin protection, and should be done before flower heads form.

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