Q: I have a plant in my lawn that spreads out like a mat in August and September. What can I do to control it?
A: You have prostrate spurge, Euphorbia supina, also known as spotted spurge, Euphorbia maculata.
It is classified as a summer broadleaf annual. That means you can control it two ways: by applying an appropriate pre-emergent chemical or by spot-spraying each clump with a broadleaf weed killer when you notice it.
Pre-emergent herbicides for spurge control in turf include pendimethalin (click for sources), dithiopyr (click for sources), and isoxaben (click for sources). Apply in late spring. You might need to make a second application 4 – 6 weeks later.
You can also spot spray in summer with a broadleaf weedkiller (click for sources) like Weed B Gon (click for sources) or Bayer Season Long Weed Control (click for sources).
The weed is also easy to pull by hand.