Common chickweed, appearing with its tiny white and purple flowers in early spring, is one of the most frustrating annual weeds that gardeners in Pennsylvania must deal with. The weed is so persistent that many people just give up and wait for it to disappear when warm weather arrives. Pesky as common chickweed is, gardeners shouldn't lose heart because it is actually quite easy to get under control. Prevention and persistence are the keys to battling this lawn and garden intruder.
Apply a granular pre-emergent herbicide in late winter, following product directions. In southeast Pennsylvania, USDA Zone 7a, this will be about the first week of March, while in northeast Pennsylvania, Zones 5a and 4b, it will be about the third or fourth week of March. Your window of opportunity is open between final snow melt and germination of the chickweed. Do this for the lawn and garden. Most pre-emergent herbicides are lawn, flower bed or vegetable garden specific, so read labels to make sure you get the right product.
Pull the chickweed that sprouts in garden beds. You can wait until they reach a size large enough to pull easily, but don't let them flower and go to seed. Alternately, use a garden hoe or handheld scraper to scrape them from their roots.
Apply a post-emergent herbicide to chickweed that sprouts in the lawn before it flowers and sets seed. Follow the label directions to avoid killing other plants.
Spread a 1- or 2-inch layer of mulch in garden beds to prevent the germination of other weed seeds later in the season and to help prevent chickweed from returning the next spring.