In the past I've mowed them first then tarp them with any kind of plastic you have and weigh down with sandbags (tires, rims, rocks, t-posts layed on top, old logs, pieces of concrete, jugs of water, pots of dirt...) and leave as long as you can. I've also done this without mowing first but you have to lay them down somehow. It's not an overnite solution but if you keep doing it consistently (year over year) you can subdue some of those weeds.We have the same problem. Our goats won’t even eat them enough to make a dent. We have about 2 acres with waist high weeds and I am trying to figure out what to do to get rid of them as they pose a high fire hazard once they die on their own. I don’t want the husband to spray roundup as he has done in the past when we didn’t have chickens. HELP!