How to Kill Canada Thistle With Lontrel


Canada thistle (Cirsium arvense) is a perennial plant in the Asteraceae family and is a weed that originated from Europe and Asia. Canada thistle grows quite tall, reaching up to 5 feet. It spreads rapidly by seed and underground root stems, and often is hard to control. Several herbicides are used to help control and eradicate Canada thistle, including Lontrel, which contains the active ingredient clopyralid. Clopyralid is a post-emergent herbicide, which means it is applied after the thistles are growing. There are several types of Lontrel, and Lontrel Turf and Ornamental usually is the best choice for the home gardener.

Step 1

Apply Lontrel Turf and Ornamental in late September, and avoid using it within two hours of an expected rain or while it is windy.

Step 2

Wear goggles, waterproof gloves and clothing that covers your exposed skin while working with Lontrel Turf and Ornamental.

Step 3

Mix 7.3 ml (1/4 fl. oz.) of Lontrel Turf and Ornamental with ½ gallon of water for every 1,000 square feet of lawn.

Step 4

Spray all the Lontrel Turf and Ornamental mixture with even sweeping motions over the areas infested with Canada thistle.

Step 5

Reapply Lontrel in the spring as the new thistles emerge. Apply half the recommend dose, such as 3.65 ml (1/8 fl. oz) of Lontrel Turf and Ornamental mixed with ½ gallon of water per 1,000 square feet of lawn.

Step 6

Discard the dead thistles that were treated with Lontrel Turf and Ornamental by bagging them up and putting them in the trash. Do not compost them.

Step 7

Wash your clothes separately from other clothes in hot water and detergent. Shower with soap and shampoo to clean your body and hair of any residual Lontrel Turf and Ornamental. Do this before you eat, drink or smoke.

Things You'll Need

  • Backpack or handheld sprayer
  • Lontrel


  • Lontrel Turf and Ornamental Label Speciman Label
  • Oregon State University: Cirsium arvense - Canada thistle
  • Government of Saskatchewan: Canada Thistle and its Control
Keywords: kill Canada thistle, Lontrel Lawn and Ornamental, kill thistles with Lontrel, Cirsium arvense

About this Author

Melissa Lewis has been a professional writer since 2005. Her work has appeared in various online publications. A former elementary classroom teacher and media specialist, Lewis is also a script writer, with a movie script, "Homecoming," she co-wrote currently in production. She holds a Bachelor of Arts in psychology.