Canada Thistle
CIARrosette


Asteraceae or Sunflower Family
Cirsium arvense

IDENTIFICATION:
Growth Habit:
Perennial, grows up to 4 feet tall.
Leaves: Deeply toothed with spines, hairy on underside, varies quite a lot from plant to plant.
Stems: Smooth to slightly hairy, branched at top.
Flowers: Small bristly cluster, 3/8 to 5/8 inches in diameter, light lavender to deep rose purple, male or females.
Roots: Extensive creeping horizontal roots up to 16 feet long and 2 to 22 feet deep.
Seeds: Produces 9,300 seeds per plant, viable up to 22 years.
Reproduction: Vegetatively from horizontal creeping roots or from seeds.
Habitat: Found in meadows, roadsides, native grasslands, pastures, and waste places.

MANAGEMENT OPTIONS:
Handpulling: Only effective on small infestations if done consistently and persistently throughout the growing season and for multiple years. Be sure to wear gloves.
Mowing: Mowing is an inconsistent method of control for Canada thistle, depending on the conditions present at the site. In some instances, mowing two to three times annually for a period of three or more years can eliminate an infestation. In other situations the same regime will only accomplish a reduced seed crop.
Biological Control: N/A
Grazing: Not recommended because livestock tend to avoid it because of its spiny stems and leaves.
Herbicide: The following herbicides are labelled for control of Canada thistle. Always consult product labels and read them carefully to ensure correct species/land management usage and chemical application.

Trade Name: Active Ingredient: Rate: Efficacy: Comments:
Tordon 22k picloram 1 qt/acre  most effective on actively growing plants; spring or fall  Cannot use near surface water, shallow water, landscaped areas and current or future vegetable gardens (Restricted Herbicide - need an applicator license to use.)
Milestone aminopyralid 5-7 oz/acre most effective in actively growing plants; spring or fall Can be applied to waters edge; cannot be used in landscaped areas and current or future vegetable gardens, mulch or manure from treated areas should not be applied to vegetable gardens or composted for vegetable gardens
Forefront aminopyralid + 2,4-D 2-2.5 pts/acre most effective in actively growing plants; spring or fall Can be applied to waters edge; cannot be used in landscaped areas and current or future vegetable gardens, mulch or manure from treated areas should not be applied to vegetable gardens or composted for vegetable gardens
Curtail clopyralid + 2,4-D 2-4 qts/acre most effective in rosette to bud stage Do not apply to shallow groundwater areas
Transline clopyralid 1-1.3 pts/acre least effective herbicide listed Do not apply to shallow groundwater areas
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