How to rid garden entirely full of thistle
We moved into a home with a 100 ' x 25 ' garden. we planted half with vine-type vegetables (squash, pumpkins) and the other half with carrots, tomatoes, peas, etc. The vine vegetables have always done well even as the weeds get out of hand and take over. The other side has been eaten 2 years in a row by rabbits, so I put a fence up and was all ready for this season. I till in the fall and spring. Since everything was eaten early last year we neglected the garden and it was entirely covered by weeds by fall, mostly thistle. This year I tilled, then forgot about it as winter continued. The thistle completely covered the garden, so 2 weeks ago I sprayed with an organic spray. Weeds were about 6" tall. It did nothing to kill them. Now they're 12-18" tall. If I could harvest them I'd be rich. I'm Ok giving up on this growing season if I focus on ridding the garden of weeds for next year, but how? I have some large, thick tarps that I thought about laying down for the season. I also have concentrated glyphosate that I use with a hose sprayer on my gravel driveway (that works well). Doing anything by hand on a garden of this size is out of the question. Do I till...or will that makes things worse? I'd like to do something before they start to bloom. Feel free to call at 612-201-7221.
Carver County Minnesota
It requires persistence to get rid of thistles. The most effective management techniques include use of a herbicide. Here are links to information about thistle management: http://extension.colostate.edu/topic-areas/natural-resources/canada-thistle-3-108/
After the herbicide treatment (please carefully follow the herbicide's label), you might want to consider putting those tarps over the area. You are likely to have to repeat the process at some point. Thistles are tenacious.
As far as tilling, we are now starting to see research that suggests that it is better NOT to disturb the soil because it damages soil structures and uncovers weed seeds.