Trifolium incarnatum

Morphological description

Annual herbaceous plant, robust and scapose, with erect stems generally reaching a height between 15 and 50 cm, but sometimes exceeding 50 cm. The stem is striated, green in color, and has a pubescent surface: the lower part is covered with patent hairs, while the upper part has appressed hairs. The plant therefore appears slightly velvety.

The leaves are alternate and trifoliate, with broadly obcordate leaflets (inverted heart-shaped), varying in size between 1.5 and 3.5 cm. The surface of the leaflets is herbaceous and pubescent on both sides, and the margins are irregularly crenate-dentate or denticulate especially in the apical half. The leaf apex is obtuse or slightly retuse. The leaves are borne on a petiole 2-4 cm long, also hairy. At the base of the petiole there are ovate, membranous, hairy and dentate stipules, which wrap the stem with two small ears, giving a characteristic biauriculation visible also from the side.

The inflorescence consists of a single terminal head, dense, ovate or ellipsoid in shape during flowering (about 1-2 cm wide by 3-6 cm long), becoming more cylindrical in the fruiting stage. The head is supported by a long, hairy peduncle, lacking bracteoles or involucre. The flowers, numerous (between 50 and 120) and hermaphroditic, are bright red, sometimes tending to pink or white in the subspecies, with a corolla typical of the Fabaceae family (standard, wings and keel). The petals are glabrous, about 10-15 mm, and slightly exceed the calyx teeth, which is campanulate, hairy and urn-shaped at fruiting. The calyx teeth are 5, herbaceous, triangular, subequal, as long as or slightly longer than the tube, with a hairy outer surface.

The androecium is composed of ten diadelphous stamens, nine of which are fused to form a tube and one free. The gynoecium has an ovary with a style that passes internally through the stamen tube.

The fruit is a legume called camara, ovoid, enclosed in the persistent calyx, with a membranous pericarp and containing a single seed of yellowish or green-brown color. The root system is not described in detail in the sources, but as with other Fabaceae, the presence of taproots with rhizobial nodules for nitrogen fixation is presumed.

Habitat and distribution

Trifolium incarnatum is widespread throughout the Mediterranean area, with a range extending from western and southern Europe to the Mediterranean coasts, with extensions northwards and eastwards. In Italy it grows spontaneously from the plains up to about 2,200 meters altitude, mainly frequenting grasslands, plowed fields, uncultivated lands and crop margins, preferring siliceous and well-drained soils.

It is a eurymediterranean species, often cultivated as forage, but also naturalized in many areas. It prefers sunny or partially sunny exposures and open environments, not excessively humid.

Flowering period

Flowering typically extends from May to July. No significant geographic variations in the period are reported, but flowering may slightly anticipate or delay depending on altitude and local climate.

Ecology and pollination

Trifolium incarnatum is pollinated by pollinating insects, particularly bees and other hymenopterans, which are attracted by the bright red color of the flowers and their typical structure. Cleistogamy (self-pollination without flower opening) is not present.

The plant produces numerous seeds, whose dispersal mainly occurs by falling near the mother plant, favored by the persistent calyx that protects the fruit. No mechanisms of long-distance dispersal such as wind or animals are highlighted.

Curiosities and traditional uses

Trifolium incarnatum is a species of great agronomic and forage importance, due to the high protein and lipid content of its biomass, making it an excellent food for livestock. It is often cultivated as a green manure crop to improve soil fertility, thanks to its ability to fix atmospheric nitrogen through rhizobial symbionts.

In the medicinal field, it is considered a medicinal species, although specific traditional uses are not detailed in the sources examined here.

The Italian name “trifoglio incarnato” derives from the bright red color, similar to flesh color (from Latin “incarnatus”, meaning “flesh-colored”), referring to the flowers.

Etymology

The genus name, Trifolium, derives from Latin and means “three leaves”, referring to the characteristic trifoliate leaf typical of many species in the genus. The specific name incarnatum refers to the bright red color of the flowers, reminiscent of flesh or incarnate color. The Italian common name “trifoglio incarnato” reflects this distinctive chromatic characteristic.

Sources

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