Answer: A heavy-duty infestation such as yours will take a couple of seasons to get eliminate. The best approach (aside from removing all the plants from your garden and going to a crop cover practice) is to mow or whack down about early summer just before it flowers. Let the new plants that come back from the roots (and they will!) grow fo another 2-3 weeks and then whack or mow them down. In another 2-3 weeks when they do it again and show their locations, start digging. Dig carefully and completely to avoid breaking or missing what seem like immortal roots. Next spring, clean up the ones you've missed. If you don't have extensive or complex plantings, consider a fabric mulch.
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