I have several acres of Tansy and the occasional hawkweed and knapweed. Yes, I am aware that Tansy has certain benefits with insects. It has however, become difficult to encourage any other growth. What do people recommend for reclaiming a Tansy field into a garden?
You might try mowing it low (before it has a chance to set more seeds), and follow up with a heavy sowing of something like buckwheat. The buckwheat is a fast growing smother crop. If you can keep the tansy shaded until first frost, you might knock it back into the manageable spectrum. Also, mow down your buckwheat before it goes to seed, or you'll be back here next spring asking how to get rid of a buckwheat field.
Hello fellow Jason, I fought this same battle last season with some good success. I had a field almost entirely covered in solid tansy. I started in the late winter by cutting down all the dead tansy sticks which made an awesome and quick bonfire (which to my surprise became a morel patch this spring). The Tansy was fought by continuous mowing which allowed the grasses to take over. Sure it's just switching one mono-crop for another, but the tansy couldn't compete once mowed for a few months. I've almost eliminated it, other than the few plants that continue to come up in the rows, but I'm actually keeping a patch this year to use as a mulch and to try some of the recipes in Sepp Holzer's book. The tansy leaves smell really interesting, especially when cut but these plants are quite persistant, and will grow from bits of root if tilled.