What is this “weed”?
Good morning. This is called hairy bittercress (Cardamine hirsuta). It is an annual weed that thrives in the cool spring weather. Eventually the plants die down when the weather gets warm, but they are notorious for their effective seed dispersal prior then! Here is our webpage about this plant and how to manage it in a lawn, https://extension.umd.edu/hgic/topics/hairy-bittercress
In addition, the Brooklyn Botanic Garden has a good article that goes into further detail about hairy bittercress, https://www.bbg.org/news/weed_of_the_month_hairy_bittercress
Thank you, Christa!