How to Kill Spurge (Spotted and Prostrate Spurge)

Triclopyr is the most effective active ingredient for spurge, and the strongest products combine it with others for a multi-angle kill. For a Long Island homeowner, the best unrestricted choice is Monterey Spurge Power, a three-way of MCPA, triclopyr, and dicamba that is literally formulated and named for spurge and is safe on cool-season lawns (bluegrass, fescue, rye, bent). Mix it at exactly 1 fluid ounce (2 tablespoons) in 2 gallons of water per 1,000 square feet, use 1.25 ounces for tough mature mats, and do not add a surfactant because it already has one. A solid legal backup is Ortho Weed B Gon Chickweed, Clover and Oxalis (8 percent triclopyr), mixed at 1 fluid ounce per gallon per 200 square feet. The strongest products of all are the professional 4-way combos like T-Zone and Triad TZ, but T-Zone is restricted in Nassau and Suffolk and Turflon Ester is commercial-applicator-only in New York, so most homeowners here use Spurge Power. Whatever you choose, spray young plants on a calm day under 90 degrees, and prevent next year's crop with a pre-emergent barrier and a thick lawn.

Monterey Spurge Power is mixed at 1 fluid ounce (which is 2 tablespoons) in 2 gallons of water to treat 1,000 square feet, so that works out to half a fluid ounce per gallon. For tough, mature spurge you can go up to 1.25 fluid ounces per 1,000 square feet. The water is just a carrier, whether you use 2 gallons or up to 5, the important thing is that you apply 1 to 1.25 fluid ounces of product per 1,000 square feet. To mix, fill your sprayer about halfway with water, add the measured Spurge Power, then top off with the rest of the water and shake to blend. Do not add a separate surfactant, Spurge Power already contains one and adding more can injure your grass. And respect the annual limit: no more than 1.47 fluid ounces per 1,000 square feet per year, and no more than 2 applications, spaced at least 21 days apart. Measuring your treatment area first (length times width) lets you mix the exact amount and avoid both under-dosing, which fails, and over-dosing, which wastes product and can hurt the lawn.

The single most reliable test is to break a stem: spurge bleeds a distinctive milky white sap (latex), while purslane and knotweed do not. That sap is your positive ID every time. Beyond that, spurge grows as a flat mat radiating in a circle from one central taproot, with small oval leaves arranged in opposite pairs, and spotted spurge has a small maroon-red spot in the center of many leaves. Purslane, by contrast, has thick, fleshy, succulent leaves and stems (spurge's are thin and wiry), and knotweed has a papery sheath at each leaf node and no milky sap. Getting the ID right matters because it confirms you are dealing with a summer annual that triclopyr handles well. One safety note: spurge's milky sap is a skin and eye irritant, so wear gloves and avoid touching your face while checking or handling it.

Two reasons. First, spurge is an incredibly prolific seeder, a single plant can produce thousands of seeds and run through multiple generations in one summer, so if any plants mature and seed before you kill them, they reload the soil seed bank for next year. Second, and more importantly, spurge is an opportunist that specifically colonizes thin, bare, hot, and compacted ground, the driveway and sidewalk edges, the worn strips, the weak spots in your turf. If you kill the visible spurge but leave those openings, new spurge simply germinates from the seed bank into the same bare soil. Breaking the cycle requires prevention: lay a pre-emergent barrier (spurge is on the label of common pre-emergents like prodiamine and pendimethalin), overseed and thicken the thin spots so there is no open ground for it to invade, and mow tall to shade the soil. Kill plus prevent is what actually ends a recurring spurge problem.

Kill spurge while it is young and small, which on Long Island generally means late spring through summer, as soon as you spot the little mats forming. Timing matters enormously because spurge changes fast: young, tender seedlings absorb herbicide readily and die quickly, often in a single application, while a mature plant develops a waxy coating that sheds spray and needs the higher rate plus a second pass. Just as critical, spurge seeds rapidly, so every day you wait, a maturing plant is closer to dropping thousands of seeds that become next year's infestation. Beyond the plant's age, apply on a calm day when the air temperature is below 90 degrees, since spraying above 90 stresses the lawn and volatilizes the herbicide. Do not mow for a day or two before and after treatment, and do not water for 48 hours after, so the plant has leaf surface to absorb the herbicide and time to move it down to the roots.