Corn speedwell

Corn speedwell is a small, weak, low-growing broadleaf with finely hairy leaves and stems. The lower leaves are rounded with toothed (scalloped) margins, while the upper leaves are smaller and more pointed. It produces tiny, light-blue to violet flowers that are nearly stalkless and tucked in the leaf axils, followed by distinctive heart-shaped (notched) seed capsules that are a key identifying feature of the speedwells. The plant is delicate and inconspicuous, forming low, sprawling growth in thin turf, and the combination of hairy foliage, axillary stalkless flowers, and heart-shaped capsules distinguishes it from the prostrate, node-rooting creeping speedwells.

Corn speedwell colonizes thin, open areas of turf with low, sprawling growth that fills the gaps a healthy stand would otherwise occupy, becoming most noticeable in spring when it greens up and flowers ahead of the turf. While individually small, dense patches detract from lawn uniformity and indicate a weak stand, and the prolific spring seed set ensures the weed returns each fall, perpetuating the problem in chronically thin turf.

Corn speedwell is a winter annual that reproduces by seed. Seeds germinate in late summer through fall, and the plant grows slowly through any mild winter weather while remaining largely dormant in cold periods, then resumes active growth and flowers and sets seed in spring before dying as temperatures rise in late spring and early summer. It completes its cycle quickly and produces abundant seed, replenishing the soil seed bank to ensure re-infestation the following autumn.

Corn speedwell thrives in thin, open turf and is adaptable to a wide range of conditions, growing in moist or dry soils and in full sun or shade. It exploits gaps in a weak or sparse canopy, where its low, spreading growth can establish without competition. Because it germinates in the cooler conditions of late summer and fall and grows through the cool season, it is most problematic where the desirable stand is thin going into winter, filling in open areas and becoming conspicuous in spring.