Common self-heal (Prunella vulgaris)

Synonyms: Brunella vulgaris, Prunella pennsylvanica

Common Names: Self-heal, heal-all, woundwort, heart-of-the-earth, carpenter's herb, blue curls

Description:

Common self-heal (Prunella vulgaris) is a low, creeping perennial in the mint family found across North America and much of the world [1][2][3]. It is a familiar little plant of lawns, paths, and moist open ground, known for its short, dense, purple flower spikes and its long history of folk-medicine use ? the names "self-heal" and "heal-all" come from that use [1][2]. MISIN tracks the introduced European form as a lawn and turf weed, though self-heal also includes a form native to North America (see Ecological Impact) [1][2].

Habit:

Common self-heal is a low, mat-forming perennial, usually only a few inches to about a foot tall, with creeping stems that root where they touch the ground and spread into patches [1][2]. Like other mints it has square stems and opposite leaves; the leaves are oval to lance-shaped, a couple of inches long, with shallow teeth or nearly smooth edges [1][2]. Its flowers are the giveaway: they are packed into a short, dense, blocky spike at the stem tip ? roughly thumb-sized ? made of small, two-lipped flowers that are usually purple to blue-violet (sometimes pink or white), each with a hooded upper lip and a fringed lower lip [1][2]. After bloom, the brown, bristly flower head often stays on the plant [2].

It is easiest to spot in summer and early fall (about June to October), when the squat purple flower spikes stand just above the low mat of foliage in lawns, trail edges, and damp clearings [1][2]. The square stems, opposite leaves, and dense blocky flower head separate it from the grasses and broadleaf weeds around it [1][2].

At-a-glance cues:

1. Low, mat-forming mint with square stems that root where they touch the ground [1][2]
2. Opposite, oval-to-lance-shaped leaves with shallow teeth [1][2]
3. Short, dense, blocky flower spike (about thumb-sized) at the stem tip [1][2]
4. Small two-lipped flowers, usually purple to blue-violet, with a hooded upper lip [1][2]

Leaves:

1. Arrangement: opposite, in pairs along the stem [1][2]
2. Shape: oval to lance-shaped, up to about 2? inches long [1][2]
3. Margin: shallowly toothed to nearly smooth [1][2]
4. Surface: green, variably hairy; stalked, the lower leaves larger [1][2]

Stems:

1. Habit: a low, creeping perennial that roots at the nodes and forms spreading mats, with flowering shoots a few inches to about a foot tall [1][2]
2. Cross-section: square, often branched, sometimes reddish [1][2]
3. Surface: variably hairy [2]

Flowers:

1. Color: usually purple to blue-violet, sometimes pink or white [1][2]
2. Shape: small, two-lipped (bilabiate), with a hooded upper lip and a fringed three-lobed lower lip [1][2]
3. Arrangement: packed into a short, dense, blocky terminal spike about 1?2 inches long [1][2]
4. Bloom time: summer into fall, about June through October [2]

Fruit and seeds:

1. Fruit type: a dry fruit that splits into four small nutlets, held in the persistent brown flower head [1][2]
2. Seeds: one seed per nutlet [2]
3. Dispersal: by seed, which moves in soil and on mowers, tools, and feet; the rooting stems also spread the patch in place [1][2]

Habitat:

Common self-heal grows nearly worldwide and is found across North America [1][3]. Its origins are mixed: a form of the plant is native to North America, while a European form has also been introduced and naturalized, so the two now grow side by side (see Ecological Impact) [1][2].

It grows in sun to partial shade on moist soils and tolerates mowing and foot traffic, which lets it persist in turf [1][2]. Look for it in lawns, along paths and trails, in fields and pastures, in open woods and clearings, and along roadsides and shorelines [1][2].

Reproduction:

Common self-heal spreads in two ways a homeowner will recognize. It sets seed in its dense flower heads, and that seed moves in soil and on mowers, tools, and shoes ? which is how it turns up in a new lawn or bed [1][2]. Its creeping stems also root wherever they touch moist ground, so a patch slowly widens on its own and forms a low mat [1][2].

It is a low perennial that comes back from its rooted stems each year and flowers from summer into fall [1][2]. Because it hugs the ground, it tolerates mowing and persists in turf [2]. For control where it is not wanted, the key is to pull or dig the rooted mats and to remove flower heads before they ripen seed [1][2].

Impact and Damage:

For homeowners, common self-heal is a minor lawn weed rather than a hazard. It is not known to be toxic ? it has a long history of use as a medicinal and edible herb ? and the trouble it causes is cosmetic: it forms low patches in lawns and beds and persists through mowing, mixing into turf [1][2]. Its small purple flowers are visited by bees and other pollinators, so many people leave it in place as a low-care groundcover [1].

For natural area stewards, common self-heal is a low-level concern, and the picture is complicated by its origins. North America has its own native form of self-heal, while a European form has also naturalized here, and the two are hard to tell apart and grow together [1][2]. Because a native form belongs in local plant communities and the plant is valuable to pollinators, self-heal is not an aggressive habitat invader, and removal in natural areas is rarely warranted ? the main reason to manage it is as a turf weed near people [1][2]. Confirm which form is present before treating it as unwanted [1][2].

Similar species:

Common self-heal is one of several low, creeping mints with purple flowers, and they are easy to mix up. Its surest marks are its square stems, opposite leaves, and short, dense, blocky flower spike [1][2].

Common bugle (Ajuga reptans) is a low mint that forms similar mats with blue-violet flower spikes. It is told apart by the way it spreads ? bugle creeps on above-ground runners (stolons) ? and by its flowers, which are arranged in spaced whorls up an open spike rather than packed into self-heal's short, dense, blocky head; its leaves are often glossy and barely toothed [1].

Ground ivy (Glechoma hederacea) is another low, creeping mint of lawns with purple two-lipped flowers. It is distinguished by its rounded, scalloped leaves and by its flowers, which sit in small clusters where the leaves meet the trailing stem rather than in a dense terminal head [2].

Cut-leaved self-heal (Prunella laciniata) is a close relative with the same blocky flower head. It is separated by its upper leaves, which are deeply cut (pinnately lobed), and its flowers, which are usually pale yellow-white rather than purple [1].

Monitoring and rapid response:

Signs to watch for:

1. A low, creeping mat of square-stemmed, opposite-leaved plants in lawns, paths, and moist open ground [1][2]
2. Short, dense, blocky purple flower spikes standing just above the foliage, summer into fall [1][2]
3. Brown, bristly flower heads persisting after bloom [2]

What you can do:

1. If you want it gone from a lawn or bed, pull or dig the rooted mats while the soil is moist, lifting the creeping stems so it does not regrow [1][2]
2. Remove the flower heads before they ripen seed, and bag flowering or seeding material rather than composting it [1][2]
3. Keep turf dense and healthy so seeds and runners have less open ground to colonize [2]
4. Consider leaving it where it is welcome ? its flowers feed bees and other pollinators, and a native form of self-heal belongs in local plant communities [1]
5. For natural areas, confirm whether the plant is the native or the introduced form before any removal; self-heal is generally a low priority and is often left in place for its pollinator value [1][2]

When to call a professional:

1. Large or persistent stands in turf where hand removal cannot keep up [1][2]
2. Situations where you are unsure whether the plant is the native or introduced form and want help confirming before deciding to manage it [1][2]
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Native Plant Trust, Go Botany. Prunella vulgaris (common selfheal / heal-all). gobotany.nativeplanttrust.org
2. Minnesota Wildflowers. Prunella vulgaris (Self-heal). minnesotawildflowers.info
3. Plants of the World Online (POWO), Royal Botanic Gardens, Kew. Prunella vulgaris L. powo.science.kew.org

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