Cirsium arvense
broadleaf weedUSDA zones 2–8Active: spring, summerAggressive perennial with an extensive root system that spreads by underground rhizomes. Produces spiny leaves and lavender flower heads.
Deeply lobed leaves with sharp spines; smooth stems (unlike bull thistle); clusters of small lavender-pink flower heads.
Mow before flowering to prevent seed spread. Repeated defoliation weakens the root system over time.
When: Mow every 7-10 days during active growth
Horticultural vinegar (20%) kills top growth. Requires repeated applications to exhaust roots.
When: Apply every 2-3 weeks during growing season
Systemic herbicide that translocates to roots. Most effective control method for established patches.
When: Apply in fall when plant is storing energy in roots for best systemic kill
Active ingredient: Triclopyr — e.g. T-Zone, Millennium Ultra 2
Grass safety: always match herbicides to your grass species — products safe on Kentucky bluegrass can kill St. Augustine or centipede. Lawn Guardian checks this automatically against your lawn profile.
Lawn Guardian turns this guidance into a schedule timed to your USDA zone and this week's actual weather — and adapts every time you log what you've done.
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