Cultural Control of the Canada Thistle
(Cirsium arvense)
Cattle, Sheep, and Goats: Each animal will eat the weeds instead of the grasses when the thistles are tender. They eat the young thistles which are still tender in the early spring. After grazing, follow up with a fall herbicide. They don't usually eat them later because of the spines. (1,4)
Tilling (Plowing): Tilling before seeding will cut emerging shoots which will slow them down. Tilling after seeding will have no effect. If you till in the fall you will decrease the weed's food reserves. Till after the crop is harvested and again every time the shoots reach 10 cm until it freezes. This will help control the weed. (2)
Hand Pulling: Hand pulling will cause more weeds to sprout. If you pull them repeatedly this will starve the roots. This works best where there is another crop to compete with it which will help to kill the weed. (1) Wear gloves!
Controlled Burning: Late spring burns work the best (May -June) while early spring burns help the weed by causing more reproduction and increased sprouting. The late spring burns work best if they are repeated every year for about 3 years. (1)
Seeding/Reseeding: To compete with and effectively kill Canadian thistle you should seed perennial crops early. Crops that work the best are alfalfa and crested wheat grass. These will compete with the weed for food and water which will starve the weed and kill it. The crops are most effective if you combine them with regular cuttings, 2 or more each season. (1,2)
Vinegar: You can inject apple cider vinegar or plain white vinegar into the center of the thistle. The roots and everything shrivel up and die. You have to be careful because vinegar can sterilize the surrounding soil. (3)
Grazing Methods: Sheep and goats eat the young thistles.Cattle also eat the young thistles. Later in the season you can put salt on them. This allows animals to eat them and they trample the plants. This doesn't kill the plant but if it is done at the right time seed production can be decreased. (1, 4)
Shading: because Canada thistle grows poorly in low light, covering them with tar paper, sheet metal, or boards can be an effective control in some situations. (5)
Links:
1) Characteristics of Canada thistle, history, and alternative weed control
2) Canada thistle control info
3) Characteristics and how to kill Canada Thistle
4) Information about Canada thistle
5) Description and Pictures of Canada Thistle
6) Profile of Canada thistle
7) General Information about Canada Thistle
8) General Description of Canada Thistle
9) Canada Thistle Fact Sheet
10) Canada Thistle-Cirsium Arvense
Pictures:
From Left: Flower heads, Flowerheads, Seedheads.
Used by permission of The Nature Conservancy's Wildland Invasive Species
Program. http://tncweeds.ucdavis.edu/esadocs/cirsarve.html
Bibliography:
1) Elpel, Thomas J., Wildflowers and Weeds Home Page. Cirsium arvense--Canada Thistle: Weed characteristics, history and uses, plus alternative weed control. [Online] Available http://www.3rivers.net/~tomelpel/weedsinfo/Cirsium_arvense.htm Revised-December 28, 2001. e-mail:thomas@hollowtop.com2) Alberta Agriculture, Food, and Rural Development. Canada Thistle-Cirsium arvense. [Online] Available http://www.agric.gov.ab.ca/pests/weeds/64010010.html Revised-December 6, 1995. e-mail: duke@gov.ab.ca
3) Golden Harvest Organics. Weed Wars: Weed ID page (Canadian Thistle). [Online] Available http://www.ghorganics.com/page23.html#Canadian Thistle January 8, 2002 e-mail: info@ghorganics.com .
4) Canada Thistle Identification and Management. Integrated Weed Management recommendations for Canada Thistle. Canada Thistle. [Online] Available http://www.colostate.edu/Depts/CoopExt/Adams/weed/pdf/Canada_thistle.pd
(5) Noxious Weed IVM Guide. Canada thistle. [Online] Available http://www.efn.org/~ipmpa/Noxcthis.html
February 23, 2007. phone:303-637-8115.
February 26, 2007. e-mail: ipmpa@efn.org.
By: Brianna Patacini - 01/2002. Updated by: Ashley Woody - 2/26/07.
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