Joel asked the question of how we control thistles, and then mentioned that he has done little more than chase them around his farm by hacking and whacking. I believe that says a lot about thistle management. I have read that thistles are bi-annuals, and I suppose that means that if we controlled them completely for about three years we would have them eliminated on our farm. That’ll never happen
We have managed them pretty well in the last 10 years through routine mowing of paddocks where they proliferate. Spraying hasn’t been a satisfactory option, as anything that slows down the thistles also slows down any good legume that would replace it. It’s very apparent that the wind plays a critical part in their spread, as anytime we allow thistles to go to seed they soon appear in an area to the northeast of their former location. (Southwest winds are prevalent here in Indiana.)
We detest clipping paddocks and avoid it every time we can. But, after a very dry 1999 where almost no clipping was done, we found ourselves in 2001 with a very healthy crop of Canada and Bull thistles. Scott and I remembered that we had let many, very short thistles go to seed in 1999, and perhaps we were now paying the price of that leniency.
Milk prices being good this year, we decided to invest in some new iron. (Maybe it’s OK for this reason.) The old 7-foot sickle bar mower was in bad need of replacement, so we purchased a new 9-foot, three-point disk mower. WOW!!! It cuts good, as fast as we can travel, and with a set of topping shoes it does a good job of doing a 4-inch theoretical cut with no windrowing of residue. That also gets it traveling over lots of our smaller rocks without too much damage. and we can usually see the big ones after the cows have grazed. It’s also low enough to just clear under our one-wire, high-tensile fence, so the only places the thistles have a chance is around the bases of the posts. Most of those are eliminated by carrying a good weed whacker with a disk cutter on the quad when we do our pasture evaluations.
I haven’t seen or heard of anything that works better. so we’ll see how it goes. Of course another dry summer could cause us to get lax with clipping again, and we’re back to square one. We’ve promised ourselves that we’ll let no more thistles going to seed. Well, it’s a nice goal anyway!