Prunella vulgaris L., Selfheal

Account Summary

Growth form and preferred habitats

P. vulgaris is a very common, widespread, almost ubiquitous, shallow-rooted, stoloniferous, flat rosette-forming, wintergreen, patch-forming perennial. It has a branching, prostrate stem from which arise both leafy and flowering shoots, generally in the range 8-25 cm tall, but rarely stems reach 60 cm (Garrard & Streeter 1983; Sell & Murrell 2009).

Prunella vulgaris occurs in a wide range of habitats and is especially frequent in short turf, damp meadows, pastures, hedgerows, open areas by tracks or on the margins of woods or scrub, rough grassy roadsides, around rock outcrops and on waste ground up to altitudes of around 750 m (Garrard & Streeter 1983; Grime et al. 1988, 2007). The plant is largely restricted to moist, moderately fertile, less acidic soils of pH above 5.0 and it is easily shaded out by taller growing herbs in less disturbed vegetation.

P. vulgaris is a particularly common, aggressive patch-forming weed in regularly mown, closely grazed, or trampled permanent grassland, such as pastures, lawns, parkland and roadside verges (Salisbury 1964; Grime et al. 1988, 2007). The nutlets (ie achenes, single-seeded dry fruits) of Selfheal were a common contaminant of commercial agriculture Clover seed mixtures in past years (Salisbury 1964), which helps to explain the species almost ubiquitous distribution in B & I and further afield.

P. vulgaris is also extremely tolerant of heavy grazing pressure and moderate levels of trampling, allowing it to become common and often abundant in short or open turf of older pastures and, for the same reasons, it is also a common lawn weed. Individual leaves and stems are short-lived and, like Trifolium repens (White Clover), P. vulgaris is rather mobile in pastures, expanding into gaps in the turf on a ± temporary basis, until ousted by more robust, competitive species. Leggy plants are also quite frequent in woodland conditions, although here again, they are probably not long-persistent.

Selfheal is especially associated with poorly drained, clay or loam soils, varying from moderately acid to calcareous in nature, that support short turf vegetation (Grime et al. 1988, 2007). On calcareous soils where P. vulgaris is most abundant, the flowers are often at their very bluest in colour (Salisbury 1964). Somewhat unusually for this flower family, the foliage is not aromatic and the flowers are not scented (Melderis & Bangerter 1955). The established strategy of P. vulgaris is categorised as C-S-R, meaning it displays a balance of all three principal ecological strategies, Competitor, Stress-tolerator and Ruderal (Grime et al. 1988, 2007).

Fermanagh occurrence

P. vulgaris ranks as the 27th most frequently recorded vascular plant species in the Fermanagh Flora Database, immediately following Trifolium repens (White Clover). It is also very widespread throughout the county, having been recorded in 460 Fermanagh tetrads, 87.1% of the total. This ranks it 26th in terms of tetrad frequency, again just behind T. repens in this respect!

Flowering reproduction

P. vulgaris flowers from June to September, the inflorescence being a short, dense, terminal, cylindrical or oblong spike of less than 50 violet-blue flowers arranged in six to eight whorls. Each of the tightly packed whorls contains about six bi-lipped flowers arranged between two quite large broadly-oval bracts which are green with purple margins and fringed with hairs (Salisbury 1964). As with Thymus polytrichus (Wild Thyme) and Glechoma hederacea (Ground-ivy), the flowers of P. vulgaris are of two types, small and female, or bisexual and larger on the same or separate plants (ie the plants are gynodioecious). However, unlike the other two species, the flowers of P. vulgaris are self-sterile (Warwick & Briggs 1979). The flowers in each whorl do not all open simultaneously, so that a slightly ragged looking flower-head results (Grieve 1931). Nectar is produced inside the corolla at the base of the stigma and is protected from small, crawling insects by a thick hedge of hairs placed just above it. Pollination is carried out mainly by long-tongued bees (Garrard & Streeter 1983).

An average-sized plant produces around 850 individual nutlets or schizachenes (ie single-seeded dry fruits) or 'seeds' and, with a mean germination rate of around 70%, this gives a calculated mean reproductive capacity of 600 seedlings/plant/year (Salisbury 1942, p. 162). Nutlets can pass through the alimentary canal of birds unharmed and produce seedlings on their excreta, providing an effective means of long-distance dispersal and establishment (Salisbury 1964, p. 104).

Vegetative reproduction

Established plants send out creeping stems and stolons that root and create daughter ramets. These become independent plants by the connection with the parent plant decaying and breaking down, usually within about a year or so. In this way, P. vulgaris can very easily reproduce vegetatively, spreading clonally to form ever larger, loose local patches over several years. In trampled, short-turf grasslands, plant fragments may also become detached, transported and re-established, helping to spread the species locally to some extent and adding to the reproductive achievements of seed dispersal. The relative importance of seedlings and vegetative fragments in the colonisation of disturbed ground requires further study (Grime et al. 1988, 2007).

British and Irish occurrence

P. vulgaris is very frequent throughout the length and breadth of both B & I as shown in the New Atlas hectad map. It is generally regarded as one of the most common and widespread species in the flora of B & I and, in common with the high percentage of Fermanagh tetrads in which the species is recorded, it is considered very likely that a similar degree of presence occurs across its whole B & I range (K. Walker, in: Preston et al. 2002).

European and world occurrence

This polymorphic and widespread species is thought to have originated in Europe and probably adjacent parts of Africa and Asia. In the southern half of Europe, the closely related P. laciniata (Cut-leaved Selfheal) occurs. From its native European range it has spread with agricultural man to N, C & S America, SE Asia, Australia and New Zealand. The native populations of E Asia and N America are distinguished as subsp. lanceolata (Bart.) Hult. and, in India, subsp. hispida (Benth.) Hult. occurs. P. vulgaris s.l. belongs to the circumpolar plants and the species is categorised as belonging to the circumpolar wide-temperate phytogeographical element (Hultén & Fries 1986, Map 1607; Preston & Hill 1997).

Uses

The ancients and early herbalists believed P. vulgaris to be a universal panacea for healing all sorts of ailments, but it was especially valued as one of the very best wound herbs. Grieve (1931) describes its uses as astringent, styptic (ie checks or staunches bleeding) and tonic. An infusion of the herb was useful as a gargle for treating sore throats or an ulcerated mouth. The infusion could also be used as an injection to treat internal bleeding, including for piles. The herb was also applied to fresh external wounds as an unguent (ie an ointment) or as a plaster, to stop bleeding and induce healing. Selfheal was sometimes used in conjunction with other wound herbs such as Sanicle (Sanicula europaea) and Bugle (Ajuga reptans) to dress external wounds such as cuts and bruises (Grieve 1931). P. vulgaris was also used to treat colds, respiratory complaints and heart trouble, to mention just a few of many ailments for which it was applied, especially in Ireland (Allen & Hatfield 2004).

Names

The genus name 'Prunella' may be a corruption of 'Brunella', from the German 'Bräune', meaning 'quincy' (a collection of bacterial pus between the tonsils and the wall of the throat – a rare but serious complication of tonsillitis), which it was supposed to cure (Grigson 1955, 1987; Melderis & Bangerter 1955). 'Brunella' is the older spelling of the name, which was first given by Otto Brunfels (1489-1534), one of the early German herbal writers and 'Fathers of botany' (Gilbert-Carter 1964). The Latin specific epithet 'vulgaris' simply means 'common', which in this case the plant certainly is (Gledhill 1985).

Seventeen English common names for the plant are listed by Grigson 1955, 1987), several of which like 'Heart's Ease', 'Herb Bennet' and 'Wood Sage' are more frequently applied to species other than Prunella vulgaris. Vickery (2019) goes a few better, listing 21 local names. One of these, 'Heart of the Earth' is in widespread use and, according to Britten & Holland (1886), the reason was, "it chiefly occurs on thin, poor soils, where the farmers give it the credit of eating away all the substance of the soil". The name 'Brownwort' refers back to the origin of the generic name, 'Brunella'. Names referring to carpenters such as 'Carpenter-grass', 'Carpenter's herb' and 'Proud carpenter' connect with the use of the plant to staunch flesh cuts (Vickery 2019).

Threats

None.

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