This is the worst weed in the garden this time of year. Often it sprouts in a warm spell in the winter, but doesn't flower until spring. We call it cressy and I don't know what it's proper botanical name is; I would check that out sometime. I'm told that it is quite edible, but I have such a running battle with it that eating it doesn't appeal to me. Last year I started my assault on it by trying to pull every single plant before they set seed. We have less this year, but since the seed can live in the ground for many years, I still have a lot of work to do. On a positive note, the battle with onion grass that I started about 5 years ago seems to be going in my favor. There is very little now compared to then and most of it pulls right out, partly because it is young or weak and partly because the soil in the beds is becoming so much nicer. Most of our spring weeds are annuals and not hard to get rid of, though the process is time consuming. The summer and fall weeds tend to be more perennial and much harder to deal with. More on them as they appear.