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.
Use one of the “three way” broadleaf weed killers (click for sources) on your weeds after they sprout. In the last few years, “four way” weed killers have been introduced: BioAdvanced Season Long Weed Control (click for sources) and Bonide Weed Beater Ultra (click for sources). Atrazine (click for sources) is labeled for broadleaf weed control in centipede and St. Augustine lawns.
The key is to pull or kill the weed before it drops seed, which it can do only a few weeks after germination.