Answer: Crabgrass can be difficult to control because it develops so many seeds and those seeds can remain viable for 3 or more years. So, pulling or killing the existing crabgrass will remove it from the garden temporarily, but the seeds it leaves behind will sprout and sprout and sprout. I think the best way to eliminate it is to remove your plants, pull the crabgrass out and then lay weed barrier landscape fabric over the bed. Then you can cut holes in the fabric to plant your perennials. Or, if you're careful, you can spray or brush a weed killer such as Round Up on the crabgrass - keeping it away from your perennials - and when the weeds are dead pull them out of the bed. Then broadcast a pre emergence product with a corn gluten base (Preen or Casoron, for instance) to keep crabgrass seeds from germinating. There's really no easy way to control crabgrass but the above one-two punch should help. Best wishes with your flower beds.
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