Q: Last year a weed appeared in my yard. I tried to keep it weeded and this year I put out Preen. None of the above did any good. It has come back with a vengeance. It is in my grass, my perennial garden, ground cover, etc. Everywhere! Please tell me what it is and how can I get rid of it!
A: I spend most of my summer weed chores fighting this pest: mulberry weed (Fatoua villosa). It is an annual weed, which means it can be prevented with the proper pre-emergent chemical. The best pre-emergent for broadleaf weeds is dithiopyr (click for sources). Apply the chemical in late March and again in mid-May. If you have a huge mulberry weed population, make a third application in early July.
The key is to pull or kill the weed before it drops seed, which it can do only a few weeks after germination.