Creeping speedwell

Creeping speedwell is a low-growing perennial that spreads as a dense mat of slender, prostrate stems lying flat along the soil and rooting at the nodes where they touch the ground. The leaves are small, opposite, and oval to rounded with toothed (scalloped) margins, dark green and somewhat waxy. In spring it produces small, four-lobed, bluish to lavender flowers held on slender stalks above the foliage, often appearing to cover the mat with tiny blue blooms. Unlike the upright winter-annual corn speedwell, creeping speedwell is a mat-forming perennial whose node-rooting stolons (and rhizomes) are its primary means of spread.

Creeping speedwell forms low, dense mats of dark-green, waxy foliage that crowd out turfgrass and create patches of differing texture and color, conspicuously dotted with tiny blue flowers in spring. Because it spreads aggressively by rooting stolons and fragments, infestations enlarge over time and become entrenched, and where the mats displace the stand they leave the turf thin and uneven, with the weed proving persistent and resistant to ordinary control efforts.

Creeping speedwell is a stoloniferous (and rhizomatous) perennial that spreads chiefly by vegetative means rather than seed. It forms mats of prostrate stems that readily root at the nodes, and it produces both aboveground runners (stolons) and underground runners that root and establish new plants. The species is largely self-sterile and rarely sets viable seed, so it spreads predominantly by creeping stems and especially by stem and root fragments, which means mowing and cultivation can scatter pieces that re-root and start new infestations.

Creeping speedwell favors shade, moist soils, good fertility, and low mowing heights, all of which give the prostrate, mat-forming perennial an advantage over the desirable stand. It establishes in cool, damp, shaded lawns where turf is thinner, and once present it expands by creeping stems and rooting fragments. Mowing practices that scatter clippings can spread it across a lawn, and conditions that keep the soil consistently moist and the canopy open allow it to form expanding mats that displace turfgrass.