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A variety of
thistles are found in turf. Like most, bull thistle is a biennial.
It grows over the summer months. The leaves are alternate; blades
are simple and form in a rosette. The leaves are unlobed to pinnately
lobed. The bladetip is pointed and the margins are toothed with
spines. The root is a fleshly taproot the first year and a fibrous
root system forms the second year.
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The second year of
growth, thistle stems elongate. The elongated stems have alternating leaves.
Flowers are present from June through October on the elongated stems.
The disk flowers are dark pink to purple with spined bracts. Bull thistle
spreads by seeds.
Thistles are found
throughout the United States and Canada.
Cultural Practices:
Individual bull thistle plants can be physically removed by cutting below
the crown in early spring. Bull thistle should be removed prior to bolting
and flowering to prevent seed development and distribution. Follow good
turf management practices to create a dense competitive stand of turfgrass.
Herbicide Use:
Thistles that are actively growing and in the rosette to flower stage
of growth can be controlled with a postemergent herbicide application.
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