Lawn burweed (spurweed)

Lawn burweed (Soliva sessilis), also called spurweed or sticker weed, is a low, mat-forming winter annual that stays small and inconspicuous through winter. Its leaves are opposite and finely divided into narrow segments, giving a delicate, parsley- or carrot-like appearance close to the soil surface. The truly diagnostic feature appears in spring: small, inconspicuous flowers in the leaf axils develop into clusters of spiny burs (sharp-tipped achenes) that harden as they mature, becoming the painful stickers that make this weed notorious in barefoot areas. The burs persist in the turf long after the plant itself has died.

While the low winter rosettes themselves cause little visible turf decline, lawn burweed's spring burs make affected turf painful and even unusable for bare feet and pets, and dense stands compete with desirable grass for light, water, and nutrients during establishment; the sharp burs persist after the plant dies, leaving a lingering hazard in an otherwise green lawn.

Lawn burweed is a winter annual. Seeds germinate in fall, typically from about October through December as soil temperatures cool, and the plant remains small and low through winter while building a rosette of finely divided leaves. In early spring it flowers and produces the spine-tipped burs, then matures and dies as temperatures warm; the hardened burs carry the seed and persist in the turf. Reproduction is entirely by seed, replenishing the seedbank for the next fall.

Lawn burweed is favored by thin, open turf where fall germination has room to occur, and it is a serious problem in temperate and subtropical lawns, especially across the South. Sparse, low-density stands, areas thinned by traffic or stress, and lawns lacking a competitive canopy in fall and winter are most readily colonized. Because the plant hugs the ground and escapes notice all winter, infestations are usually unnoticed until the painful burs form in spring.