Spotted Spurge: identify it, treat it, keep it out

Spotted spurge compresses an entire generation into about a month. Seed germinates in hot soil, the mat spreads flat from one central taproot, and new seed is dropping within five weeks, all summer long, wave after wave. That speed is why a spurge problem seems to appear from nowhere in August: the June plants you did not notice have already grandparented the ones you are looking at.

It is heat-seeking by design. Germination wants soil temperatures that lawn interiors rarely reach, but pavement edges hit easily, which is why spurge lines driveways, sidewalks, and curb strips. The red-spotted leaves and the milky sap when a stem snaps make identification certain (the sap also irritates skin, so wear gloves before pulling).

Spring pre-emergent at the crabgrass window suppresses the first flush, but spurge keeps germinating all summer, so the chemical barrier alone never quite finishes the job. Your real defense is shade at soil level: raise the mowing height, thicken thin areas, and spurge seed simply cannot get the hot bare soil it requires.

Give the pavement edges special attention because they are the incubator. Water and feed those strips a little better than the rest of the lawn, hand-pull any mats you see while they are small (the single taproot makes this easy and satisfying), and reseed thin edges in fall. Kill the edge habitat and interior spurge mostly stops appearing on its own.