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Invasive Plants in Minnesota

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Common Name
Lawn Prunella

 

Scientific Name
Prunella vulgaris L. subsp. vulgaris

 

Plant Family
Mint (Lamiaceae)

Garden Location
Not in the Garden

 

Prime Season
Early to Late Summer

 

 

Lawn Prunella is a non-native, invasive perennial forb growing on short, decumbent to semi-erect stems growing from 3 to 6 inches feet high on 4-angled stems. Stems usually have long white hair, particularly on the stem angles. Branching can occur but is usually restricted to within the inflorescence. It is a European cousin of our native Heal-all, P. vulgaris subsp. lanceolata.

The leaves are opposite, sparse, stalked, with hair on the undersides and on the stalk. Basal leaves are on longer stalks and are more ovate, with broadly rounded tips. Stem leaves are more oblong to lanceolate, up to 1-1/2 inches long and 3/4 inches wide, with a bluntly pointed tip. Margins of all leaves have shallowly scalloped. Bases taper to a partial wing. The upper and lower surface is dotted with hair glands, the margins have fine hair and the paler underside has longer hair on the veins.

The inflorescence is a dense conical terminal spike with auxiliary spikes sometimes rising from the upper leaf axils. These spikes elongate in flowering. The arrangement on the spike is common in the mint family. In this case, the flowers form a horizontal whorl of 6, which are arranged as 2 cymules of 3 flowers each. This arrangement is termed a 'verticillaster'. Each cymule of the spike is subtended by a broad hairy bract, green with a reddish edge. However, with the spike only at the tops of stems, this is somewhat unique in the mint family.

The flowers are 5-parted with a tubular corolla 1/4 to 1/2 inch long that has a violet to purplish upper lip that extends forward over the other parts, acting as a hood. The crest, or midvein, of this lip has fine whitish hair. The lower lip has a large fringed lobe with two smaller unfringed lateral lobes. These are white. The reproductive parts are exerted up and under the upper lip. These consist of 4 stamens arranged in two pairs, one pair, upper, longer than the other (didynamous). These have purplish filaments with purplish-brown anthers. Nestled between the upper pair of stamens is the style with a two-lobe stigma. The outer calyx is green to reddish, hairy on the edges and also has a 2-lipped form with the upper lip truncated to three short teeth and the lower lip cleft into two pointed teeth.

Seed: Mature flowers produce 4 smooth brownish-yellow seeds, encased in the persistent calyx. These drop from the calyx when ripe.

Varieties: The two subspecies of Prunella vulgaris are our native subsp. lanceolata (W.C.P. Barton) Hultén and subsp. vulgaris (shown here) which is native to Europe.

 

Habitat: Lawn Prunella in North America is found primarily in turf where there is moisture and sunlight. It can be propagated by seeds but the sprawling stem can root also. It grows from a root system of slender rhizomes.

Names: The genus Prunella is derived from the Latin prunum, meaning 'purple. More details below. The species vulgaris is used to represent 'common' as in a frequently found species. The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.

Comparisons: While the mint family verticillasters occur on a number of species, the shape and color of the spike here is not going to be confusing. The native variety (Heal-all) is taller and erect (photo below).

See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.

Full Plant

Above: The entire plant - usually no more than 6 inches long.

Below: The inflorescence is a verticillaster at stem top. Only the flowering spike rises from the decumbent stem.

Flower raceme

Below: The first photo is of the larger subsp. lanceolata, with its upright stem. The flower arrangement is the same as subsp. vulgaris shown above. Stems and leaves are hairy. Only several flowers on the spike are open at any time

Heal-all Stem Flower head

Below: Upper and lower leaf surface. The underside veins have longer whitish hair.

Leaf top side Leaf underside

Notes:

More on names: The generic name, Prunella was originally “Brunella,” from the German “breun” meaning “quinsy,” an inflammation of the mouth and throat. The plant gained prominence when military physicians used it to treat a contagious fever that raged among Imperial armies in Germany in 1547-1566. A brown coated tongue was a symptom - called “die breuns” - so that is where the Latinized name Brunella came from. Brunella and Prunella became interchangeable names.

Lore and Uses: As both subsp. vulgaris and subsp. lanceolata have similar genetics I repeat here the information provided on the subsp. lanceolata information sheet: With the blossoms having what appears to be a mouth and a throat, under the Doctrine of Signatures the plant was considered a mouth and throat healer. Nevertheless, the medicinal applications of the plant have always been very limited. The plant contains ursolic acid, which is known to have diuretic and anti tumor qualities. A useful mouthwash and gargle is made by boiling early spring leaves. It is an effective astringent, useful in stopping blood flow by taking an infusion made from the root and using this as a wash for bruises and cuts. Mrs. Grieve (Ref.#7) reports extensively on additional uses. The fresh leaves applied as a poultice also work for bites and scratches, as crushed leaves and flower spikes are astringent and anti-inflammatory. In fact, both Moore (Ref. #30) and Tilford (Ref. #39) attest that fresh juice of the plant preserved with 25% vodka or 10% alcohol can be used as a vulnerary, almost ouchless, for treating childhood wounds. Tilford also states that the entire plant is edible when young, said to have the flavor of bland romaine lettuce.

References and site links

References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.

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