Dog's Mercury (Mercurialis perennis) grows under trees and can cover a lot of surface. It is one of those plants you don't remember because it seems to have nothing special to draw your attention. Just some nondescript green.
Beginning of March the first stalks emerge. Here you can already see the flower buds.
Plants with female flowers are less common.
Here is one. It has already little globular fruits. Yes, they look like Spurge fruits. In fact, Dog's Mercury is, like Spurges, an Euphorbiaceae.