Heal-all (selfheal)
Prunella vulgaris
A low, mat-forming perennial in the mint family that tolerates close mowing and flowers with squat purple spikes in thin, moist turf.
Identification
Heal-all, also called selfheal (Prunella vulgaris), is a low, mat-forming perennial in the mint family that betrays its family with a distinctly square (four-angled) stem. The leaves are opposite, oval to lance-shaped with prominent veins and entire to slightly toothed margins, ranging from light to dark green and often flushed purple under stress. The most diagnostic feature is the flower: dense, blocky terminal spikes of small two-lipped blooms backed by hairy bracts, the upper lip hooded and purple to lavender, the lower lip whitish and fringed, appearing from roughly June through September. Plants spread along the ground by creeping stolons and root from a shallow fibrous system, so a single plant quickly becomes a patch. The square stem, opposite veiny leaves, and squarish purple flower head distinguish it from look-alike prostrate broadleaf weeds and from clovers, which have round stems and trifoliate leaves.
Symptoms & Damage
As heal-all spreads by stolons it forms creeping mats that displace turfgrass and create uneven, low-growing patches with a different texture and color than the surrounding stand; its flower spikes rise above mowed turf giving the lawn a weedy, mottled appearance, and dense colonies reduce turf density and uniformity, leaving a thinner, less resilient surface.
Biology
Heal-all is a herbaceous perennial that overwinters as a crown and shallow root system and regrows each spring. It reproduces both by seed and vegetatively by creeping stolons that run across the soil surface in every direction and root at the nodes, allowing one plant to colonize an area rapidly. Flowering and seed set occur through summer, and the small seeds add to the soil seedbank while the stolon network drives most local spread. Because it tolerates close mowing by flowering on short stalks, it can persist and even bloom below normal mowing heights.
Occurrence & Spread
Heal-all is favored by thin, weakened turf and is a vigorous colonizer of lawns kept too short, under-fertilized, or stressed. Adequate to high soil moisture supports its stoloniferous spread, and it tolerates some shade, so it commonly appears in moist, partly shaded, low-maintenance lawns and along turf edges. Any condition that opens the canopy or slows turf recovery, including compaction, scalping, and inadequate nutrition, gives it the opening it needs to establish and creep.
Favorable Conditions
Moist, shaded, thin turf and low-fertility sites; spreads by creeping stems.
Cultural Management
The most durable defense is a dense, vigorously growing stand: select an adapted turfgrass, mow at the higher end of the recommended range to shade out the low-growing weed, fertilize on a sound schedule, and water deeply but infrequently to favor turf over the moisture-loving weed. Small infestations can be removed by hand or with a knife when soil is moist, and lightly raking or brushing the turf before mowing lifts the prostrate stems and flowers so mowing and removal are more effective; relieving compaction and improving drainage and light penetration further tip the balance back to the grass.
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.