 They kill only the top growth. They don't take out the roots. So they'll burn off. You'll see really fast weed killing, the top growth. But sometimes a week later, two weeks later, they'll come back from the roots right back at you. You know, what just happened? I just sprayed you. What's going on? Here's what's happening. For annuals that come back from a seed, they're germinating right now by a seed. These are things with usually one taproot.