← All weeds
broadleafperennialDifficulty
Canada thistle
Cirsium arvense
Spiny leaves, purple flowers, and a root system that can run 15 feet sideways. One plant becomes a colony.
How to tell
- •Lance-shaped leaves with spiny, wavy edges
- •Small purple flowers in clusters
- •Grows in groups from a shared root
- •Comes back from any root piece left behind
Why it is in your lawn
Arrives in wind-blown seed from vacant lots and roadsides, establishes in thin spots.
Best window
Cut from May through September. Fall iron application.
1 · Fix the cause
- Cut every shoot at the soil line every 2 weeks all summer; starving the root takes a full season
- Mow high and feed so turf closes over
2 · Eco product
Iron HEDTA burns the top growth; combine with repeated cutting to exhaust the root.
Track the price of Iron HEDTA lawn weed killer (Natria Lawn Weed Control or Fiesta)What you are signing up for
A patience weed. Consistency beats chemistry here.
Reference only · what the truck would spray
Active ingredient
Clopyralid or aminopyralid
Typical product
Lontrel, professional-only blends
Why we do not recommend it
These persist in grass clippings and compost for years and have ruined vegetable gardens. Cutting works if you are consistent.
We never link to or price-track conventional herbicides. This panel exists so you understand what a service is selling you.