Prunella laciniata

Morphological description

Perennial herbaceous plant of modest size, generally 10 to 25 cm tall, with a scapose habit and ascending stems, simple or slightly branched. The stem is characterized by a densely hirsute surface, covered with erect and soft white hairs that give the plant a villous and wrinkled appearance, especially in the upper part. At the base it has a short and woody root, with stoloniferous development that allows its perenniality.

The leaves are arranged oppositely along the stem, with morphological characteristics varying depending on the position. The basal leaves have a petiole 1.5-2 cm long and present a lanceolate, entire blade of small size (about 1 x 2-3.5 cm). Moving upwards, the leaves become progressively more incised, often pinnatifid or with 1-2 lobes per side, until reaching an almost linear and toothed shape in the upper cauline leaves, which often surround the base of the inflorescence. All leaves are slightly hairy, especially on the back and along the veins, and have an entire or toothed margin depending on the specimen.

The inflorescence consists of dense and cylindrical verticillasters, about 2-4 cm long, placed at the top of the stem and formed by 3-9 verticillasters with 6 flowers each, arranged in compact spikes. The bracts accompanying the flowers are reniform, about 2 x 1 cm wide, with mucronate margins and reticulate veins, pale green in color sometimes slightly tinged with reddish.

The flowers are hermaphroditic, zygomorphic and tetracyclic, with a gamosepalous calyx about 10 mm long, hairy and bilabiate. The upper lip of the calyx has three slightly pronounced teeth, with the median tooth, oval and wider, ending abruptly with a mucro. The lower lip is divided in half into two lanceolate and strongly ciliate lobes. The gamopetalous corolla, 15 to 20 mm long, is white-yellowish or pale yellow, with a tube about 10 mm long. The upper lip of the corolla is helmet-shaped, keeled on the back and slightly larger than the lower lip, which is trilobed with oblong lateral lobes turned downward and a larger, denticulate central lobe. The stamens are four, didynamous, parallel and all fertile, with the two anterior ones curved forward and protruding from the corolla tube. The style is bifid with stigma divided into two acute lobes.

The fruit is a schizocarp called a tetrachene achene, composed of four ovoid-oblong, smooth and trigonous mericarps, light brown in color.

Habitat and distribution

This species is typical of European Mediterranean regions, with a range extending along the Mediterranean coasts and also present in Central Europe and Western Asia. In Italy it is common and widespread in all regions, from the plains up to about 1400 meters altitude.

It prefers habitats of poor, dry and well-exposed meadows, with particular preference for calcareous soils. It grows in arid and sunny environments, often on poor and well-drained substrates. In the Mediterranean basin it is also found in similar environments, characterized by hot and dry climates.

Flowering period

The flowering typically extends from April to August, with peaks in the summer period (June-August). In some more northern areas or at higher altitudes, flowering may be slightly earlier or later, but generally remains within the spring-summer period.

Ecology and pollination

The plant mainly relies on entomogamous pollination, with pollinator insects visiting the flowers for nectar and pollen. The zygomorphic and bilabiate structure of the corolla is suitable for attracting small insects such as bees and hymenopterans, which promote cross-fertilization.

Seed dispersal occurs through schizocarps that separate into four nutlets, facilitating local propagation. The presence of stolons and basal buds also allows vegetative reproduction and the ability to rapidly colonize open spaces.

Curiosities and traditional uses

The species is recognized as medicinal, with properties similar to those of Prunella vulgaris, from which it mainly differs in leaf shape and corolla color. Traditionally it has been used for its alleged antibacterial, antispasmodic, antipyretic, hypotensive, antiseptic, astringent, febrifuge, vermifuge, vulnerary, diuretic, stomachic and tonic virtues.

The common name “Yellow Prunella” derives from the characteristic color of the flowers, which differ from the typical violet or blue of other species in the genus. At a popular level, the plant has been used in local traditional medicines, although today it is used cautiously and mainly for informational purposes.

Etymology

The genus name Prunella, sometimes also called "Brunella", may derive from the German term “Bräune”, meaning angina, referring to the therapeutic properties attributed to the plant, or from the brown color of the calyces of the species. The specific epithet “laciniata” refers to the deeply incised or laciniate shape of the cauline leaves, a distinctive characteristic compared to other Prunella species.

The Italian common name “Cut-Leaved Selfheal” refers to the light, white-yellowish or pale yellow color of the flowers, which visually distinguishes it from the more common blue or violet-flowered brunellas.

Sources

• Prof. S. Pignatti, "Flora d'Italia"
• Acta Plantarum - Flora delle regioni italiane (scheda di Giuliano Salvai)
• Tela Botanica / H. Coste, "Flore descriptive et illustrée de la France"
• World Flora Online (WFO)