Ask Mr. Smarty Plants

There are two plants referred to by the common name "chickweed:" Stellaria media, common chickweed, and Cerastium glomeratum, sticky chickweed. This website from the University of California Integrated Pest Management on Chickweed will give you more information on the habits of the plant as well as means of control. The species are quite similar and both are native to Eurasia; therefore, they will not appear in our Native Plant Database. Although the plant is non-native, it nevertheless grows in every state in North America, as well as most of the Canadian provinces as you can see from this USDA Plant Profile Map.

As best as we were able to understand, it does its major growing in early Spring, and that is the most effective time to be weeding it out of the ground. We are assuming you are referring to planting lawn grasses which, when mature, should be taller than the approximately 4" height of the chickweed, and can therefore shade out the invasive weed. We are unfamiliar with the lawn grasses in Pennsylvania and would suggest you contact the Penn State Extension Office for Montgomery County. They should have information either online or in printed form on lawn grasses for your area, including when and how they should be planted.