Stop the surge of spotted spurge

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Spotted spurge is an annual weed species that can become a serious pest in your lawn, flower beds and even container plantings. Most people have no trouble recognizing the weed, with its small, dark-green leaves marked with a red spot midway down the center leaf vein. Spotted spurge can overgrow low-growing ground covers, invade turf grass and open areas in gardens and landscapes, and can grow in sidewalk cracks. Spotted spurge is a summer annual that depends on its prolific seed production for survival.

A single plant is capable of forming a dense mat up to three feet in diameter, producing several thousand seeds. Seeds are small and can remain dormant in the soil until conditions are suitable for germination. Seeds that are produced in summer germinate readily, but seeds produced in late fall are mostly dormant and won't germinate until spring. Spotted spurge germinates best when temperatures are between 75 and 85 degrees, but germination can occur at temperatures as low as 60 and as high as 100. When moisture is available, germination can occur from February through September throughout the San Joaquin Valley.

The primary method of managing spotted spurge should be prevention, because it is very difficult to control this weed once it is established. Avoid bringing spotted spurge seeds into uninfested areas. Use weed-free planting seed and uncontaminated planting stock. Clean your lawn mower and other garden equipment to avoid moving seeds from an infested area to a clean area in your garden. Be sure to cultivate or hand-pull new plants before they produce seed.

Plants that are hand-pulled often break at the stem, leaving the root and several buds or a single stem from which regrowth is possible. Spotted spurge seeds need light for maximum germination, so you can reduce germination by covering bare soil with a layer of mulch. When mulching, put at least an inch of a fine mulch or 3 inches of a coarse mulch (bark, wood chips, etc.) on the soil surface. Seed that gets on top of the mulch will germinate and grow there.

Hand-pull spotted spurge plants from containers or ornamental beds. There are no selective herbicides that will control spurge once it is becomes established in your flower beds. If planting new containers, be sure to use sterilized or weed-free planting mix. When purchasing container plants or stock for your flower beds and shrub borders, avoid any that may have spotted spurge infestations.

One of the best control measures for spotted spurge in turf is to maintain a competitive stand of grass. Where open areas develop in the turf either from lack of water, disease, insects or compaction from foot traffic, light is able to penetrate to the soil surface, allowing spotted spurge to germinate. Once spotted spurge is established in your lawn, changing your cultural practices (mowing height, fertilization, irrigation) will not control it. Raising the mowing height in tall fescue or perennial ryegrass to 2 inches or more can help prevent spotted spurge invasions in the first place. A pre-emergence herbicide can be helpful in reducing establishment of spotted spurge in lawn if it is applied in late winter before the weed seeds germinate.