Well they are pretty flowers! An easy way to limit their profligate habits is, just as they're running to seed, grasp the whole plant, leaves and all, then with a sharp twist, yank the whole thing out. It won't get rid of the deep taproot, new foliage will soon come in to fill the gap. Wouldn't recommend composting the seed heads either. They are easy to remove when small, but more of a challenge when established.