By John and Diane Vafis, UC Master Gardeners
Spotted spurge is one of those weeds that seem to defy our best efforts to control it. A low growing plant that develops into a dense mat, spotted spurge overgrows turf and competes with your preferred plants. It can be identified by its dark green tiny leaves, which often have a red spot about mid-way down the center leaf vein. The stem, when broken, exudes a milky, sticky latex juice. Spurge is an annual weed; it does not survive a winter. However, it is an efficient seed producer. The tiny pinkish flowers abundantly produce a three-celled seed capsule that is 1/16-inch long or less very early in its lifecycle. A mature plant will produce thousands of seeds which can spread quickly. The seeds are easily dispersed by wind. I have found it growing in containers that are 12 inches above the soil. Spurge can be very difficult to control once it becomes established, so prevention is key. However, once it invades there are some things you can do to reduce its impact.
Constantly monitor infested areas so you can pull new plants before they produce seed. Take care as you weed, since plants that you hand pull often break at the stem, leaving the root and several buds or a single stem from which regrowth is possible. It is a bit like painting the Golden Gate Bridge: once you have cleared an area, you must go back to the beginning and do it again. This repetitious weeding can be reduced by using a mulch on the exposed area. A two-inch layer of mulch on all exposed soil will prevent light from reaching the seeds and prevents germination.
If you must use chemicals, there are pre-emergent products that can slow the spread of spurge. Glyphosate is an effective herbicide to kill spurge, but it also kills any plants it touches.
Persistence is the key to controlling this weed.