How can I remove 2 acres of moderately infested former farmland containing Bull Thistle? I have an organic Permaculture farm on 1/4 acre, 3 3/4 acres are being turned into a pollinator bird insect animal friendly ecosystem. I’m cutting up all the seed heads and stems and throwing them away. My concern is in the spring they’ll regrow, I’ve been told to cut them to the ground when they flower, that will take energy out of the plant. Is there anything that will outcompete this noxious weed?

Hi Randee yes indeed thistles are a real challenge. its good you removed the seed as they can spread via wind and you end up with many more in your field. So now that they are dead they should not grow again as they are a biannual, meaning they grow leaves year 1 and in year 2 grow flowers and seeds. So in year 3 they should be done, but of course there are still more seeds waiting for the opportunity to germinate. there are 2 approaches. use 30% vinegar and spray on green parts of the thistle plants. note 30% is not salad vinegar so take care, wear gloves and dont spray on a windy day. the larger the plant the more spray coverage you will want. The other approach is to remove flowers before they set seed then plant sorghum sudan grass cover crop on the heavy side. This is a tall forage- like cover crop so it will get up to 8 feet if you let it. If that is a problem given what equipment you have you can keep it mowed to about 6 inches so not to hurt its ability to regrow. Leave this cover in all summer as it is a heat lover and will be winter killed. This is a very competitive cover crop, which is why including it in a cover crop seed mixture is difficult. So an IPM approach that is organic 1. spray all green thistles with 30% vinegar (should start to die within 24 hours). Then spray again a week later 2. plant hairy vetch when the soil is warm and you can let it grow through August. I hope this is helpful. All the best,
Vicki Morrone