Pearlwort
Sagina procumbens
A low, moss-like perennial that forms tight cushions in closely mown fine turf — greens and tees — especially where the sward is thin.
Identification
Pearlwort (Sagina procumbens) is a low, mat-forming weed that is easily mistaken for moss or a fine bentgrass at a glance. It produces dense rosettes and prostrate stems that root at the nodes, forming tight cushions of bright glossy-green foliage. The leaves are very small, narrow, awl- or needle-shaped (linear) and opposite, joined at the base around the stem, giving the plant a fine bristly look. Tiny inconspicuous white five-petaled flowers are borne singly on slender erect stalks and develop into small capsules; the wiry flower stems projecting above the mat are a key distinguishing trait that separates it from true moss, which has no flowers. Unlike moss it has a fibrous taproot system and the foliage carries a slightly waxy coating that sheds water and helps it resist some contact herbicides.
Symptoms & Damage
In turf, pearlwort forms tight green cushions and mats that crowd out desirable grass, creating an uneven, lumpy, mossy-looking surface that disrupts ball roll on fine turf and degrades overall uniformity. As patches enlarge and merge they displace the stand, and because the dense low mat tolerates very close mowing it persists where grass thins, leaving a weedy, patchy appearance and reduced playing or aesthetic quality.
Biology
Pearlwort behaves as a low-growing perennial (sometimes acting as a winter annual in colder areas) that reproduces both by abundant seed and vegetatively by stems that root at the nodes wherever they touch moist soil. It is an extremely prolific seeder, and the long-lived seedbank can persist for several years, allowing repeated reinfestation. Seedlings establish readily in cool, moist conditions of spring and fall, and the spreading rooted stems let an established patch enlarge steadily through the growing season.
Occurrence & Spread
It thrives in cool, persistently moist, compacted situations and is strongly favored by frequent irrigation, poor drainage, and shade. Pearlwort is a classic problem of closely mowed, intensively watered turf such as golf greens, tees, and other fine turf, as well as in pavement cracks, gravel, and bare moist soil. Thin, low-fertility, or overwatered stands give it the open, damp microsites it needs to invade and colonize.
Favorable Conditions
Moist, frequently irrigated, closely mown fine turf with thin or bare areas; compaction.
Cultural Management
The most effective long-term approach is to correct the conditions that favor it: improve surface and internal drainage, reduce irrigation frequency to avoid continually wet surfaces, relieve compaction through aeration, and increase light penetration where shade contributes. Maintaining dense, vigorous, properly fertilized turf at the correct mowing height helps the grass outcompete pearlwort, and small or newly noticed infestations can be hand-removed or dug out promptly before they spread, since established merged patches are far harder to manage.
Further Reading
University extension resources — open in a new tab.
Related Reports
No published reports yet for this pest.
Reports will appear here as they are peer-reviewed and published.