ASK Jeff: The Rodale Institute’s farm manager, Jeff Moyer, answers your hardcore farming questions

How do I get rid of Canada thistle?

Posted July 13, 2006

What Jeff brings to the table

Jeff Moyer, who’s been the farm manager here at the 333-acre Rodale Institute research farm for more than a quarter of a century, receives lots of mail from farmers just like you asking for advice. Jeff’s hands-in-the-dirt experience over the past 26 years has run the gamut from refining the farm's cover cropping and crop rotation systems (including managing 270 acres in a rotation of corn, small grains, hay, and edible soy beans for a Japanese market) to overseeing The Rodale Institue Farming Systems Trial®, the world’s longest running side-by-side comparison of organic and conventional agriculture. We thought it would be fun and informative to share some of these farmer-to-farmer exchanges, and Jeff’s practical wisdom, with our readers … and we’ll be doing it on a regular basis.

Got a question of your own? Click here to send it to Jeff.

Dear Jeff,

How do you get rid of Canada Thistle in an organic system?

Roger Rivest
Ontario, Canada

Dear Roger,

Thanks for the email and the tough question. Perennial weeds are the hardest to remove from fields organically. In many cases, they are there because of past practices based on chemical herbicides that worked well to eliminate pressure from annual weeds but open the door for perennials to move in and take hold. Of the perennial weeds, Canada thistle is one of the toughest. Crop rotations that favor row crops where cultivation can rip them out, and hay or forages where cutting and chopping can weaken their roots can help. Small grains can be a nightmare, because there are few opportunities to have any meaningful management measures.

If the problem is serious, you may need to take more drastic steps and actually take the area out of production for a year and use more intensive management strategies. We have found that a system of rotating rye and buckwheat has had the best success. We start by planting rye in the fall after your crops are harvested. Then, in the spring—as early as possible—till in the rye and plant buckwheat, till in the buckwheat once it begins to bloom and plant buckwheat again, repeat again with buckwheat if possible, then plant rye again in the fall. By the following spring, you should see a great improvement. The constant tillage and planting of cover crops weakens the root system of the thistle plants. This system seems to work, although you will loose production of marketable crops for one season while you spent 18 months on the program.

Good luck and let us know how it works.