Over one season a clump of crab grass can produce as many as 8,000 weed seeds, and some weed plants can produce a quarter of a million seeds in one season. Weed seeds travel by various means to reach their final growing destination. Some of these ways are through bird droppings, runoff from drains or nearby hills or slopes in yards, grass seeds and mulch and by air. Not all weeds are bad, however. Some weeds offer nests to beneficial insects who eat the insects that are harmful to your lawn or garden.
Weeds also control erosion and break up soil with their extensive root system.
No matter what you do, weeds are inevitable.