Welcome to Just Answer and thanks for your question. The best way is to just remove it with a fork or shovel after a good rain. It comes up readily with roots intact. If you have scads of it, then a brush killer like http://www.bayeradvanced.com/tree-shrub-care/products/brush-killer-plus will get rid of it, but be careful. It will also get rid of anything else it comes in contact with.