March to April
Purple or Red Deadnettle (Lamium purpureum) of the mint family
Eating Green -- harvest the young leaf shoots in the Spring and use within salads or smoothies or use as a tea. This weed easily reproduces from seed or pieces of plant. Chopping it up can increase the number of plants. Pull it roots & all to better rid you plot of this colorful but weedy 'groundcover'.
Hairy Bittercress (Cardamine hirsuta) is another weed that is blooming and seeding up right now. It's a very invasive weed and the tiny seeds can be expelled several yards from the pod at maturity. Its delicate little white cluster of flowers sit tall on erect stems above the base of its leaves. This member of the mustard family is edible as a bitter herb.
The 3 Foragers has hints on gathering and eating. A video by Wildman Steve Brill is included.
And, this is definitely not an edible weed, as chronic exposure can cause irreversible liver damage.