Hello; Thanks for submitting your garden and landscape questions to Ask Extension. The weed identified in your photo is chickweed which is a winter weed that will soon be spreading seeds in your garden and waste places to germinate in fall and become the weed in spring. See University of Maryland Extension publication https://extension.umd.edu/resource/common-chickweed. In flower and vegetable beds dig chickweed and other weeds with a garden fork or shovel and dispose into yard waste for county pick-up. Knock off dirt from roots before disposing weed matter into bags/containers. Dig up as much of the root mass for disposal too. 

To control weeds in turf focus your efforts to grow healthy turf by setting your lawnmower to its highest setting so that grass is cut a minimum 2"-3" height, over-seed bare patches and cover with a light dressing of straw, or put down sod. See University of Maryland Extension publication https://extension.umd.edu/resource/lawn-care.

Final comment: chickweed will disappear as warm weather settles in. It is a cool season weed only. And controlling chickweed is much, much easier to do than dealing with Japanese Stiltgrass!

Thanks; Christopher 
 

Japanese stiltgrass is already germinating now. The seeds start to germinate a little bit earlier than crabgrass when the soil temperature is around 55F. On our website, there are photos that show the different stages of Japanese stiltgrass growth (including what the seedlings look like). This page also has information on how to control it in a lawn. https://extension.umd.edu/resource/japanese-stiltgrass

Christa