Euphorbia peplus

Morphological description

Annual herbaceous plant, latex-bearing and glabrous, with height varying between 10 and 40 cm. The stem is cylindrical, often ascending or prostrate, with a branched habit, especially at the base, from which secondary stems arise. The root system consists of a taproot.

The leaves are alternate, soft and herbaceous in texture, with an obovate or elliptical blade, measuring between 5 and 25 mm in length and 4-15 mm in width. They are entire, with a smooth margin, attenuate or cuneate base, and obtuse or emarginate apex; the petiole is about 1 cm long and the lower surface shows a slight glaucousness. The lower leaves tend to fall off early.

The inflorescence is a pseudoumbel (pleiocasia), terminal and composed of 3-5 rays, frequently forked from 2 to 8 times, with bracts similar to the upper leaves but slightly larger and often mucronate. The cyathium, small (0.7-1.5 mm), is subsessile and has two bracts at the base that simulate a perianth. Inside the cup-shaped structure are the male flowers, reduced to a single stamen each, and a pedunculate female flower. There are four nectaries of greenish-yellow color, sometimes with reddish shades, elliptical or subulate crescent-shaped, with two white appendages shaped like filiform horns.

The fruit is a subglobose schizocarp, measuring 1.3-2 × 1.5-2.2 mm, composed of three monospermous mericarps (cocci) smooth, longitudinally winged on the back by two keels and glabrous. The seeds are ovoid, grayish-white in color, with a hexagonal section and present longitudinal and round pits on the surface; the caruncle is rounded and deciduous. The capsule is pendulous, ovate-triangular and two-winged along the back.

Habitat and distribution

It is a cosmopolitan species, widespread throughout the Mediterranean basin and in many other temperate areas of the world. In Italy it commonly grows in anthropized environments such as cultivated fields, vegetable gardens, pastures, gardens and nitrogen-rich places (nitrophilous environments), often in the presence of moist or moderately moist soils. It prefers sunny exposures and is found from the plains up to about 1700 meters of altitude.

Flowering period

The flowering period is prolonged, extending from January to December, with local variations related to climate and latitude. In milder Mediterranean climates it is possible to observe flowers for most of the year.

Ecology and pollination

The species is an annual herbaceous plant that reproduces through seeds produced by cyathium inflorescences, a particular inflorescence typical of Euphorbiaceae. Pollination is mainly entomogamous, favored by pollinating insects attracted by the nectaries present in the glands of the cyathium. The cyathium structure, with male and female flowers gathered in a cup, facilitates cross-pollination.

Seeds are mainly dispersed through mechanisms of fall and local dispersion; the presence of caruncles, lipid-rich structures, suggests that ants and other small insects may also contribute to secondary dispersal (myrmecochory).

Curiosities and traditional uses

This species is known for its toxicity: it contains irritating latex and chemical compounds such as flavonoids, tannins, anthraquinones, sterols and triterpenes toxic to humans and animals. Historically it has been used in herbal medicine as a purgative, expectorant, anti-inflammatory and antipyretic. However, its use is strongly discouraged due to its high toxicity, with risks even from simple skin application or contact with eyes and mucous membranes.

Recently, studies are underway to investigate the potential antitumor properties of its latex and bioactive compounds, but such uses are still experimental and unofficial.

The common name “Petty Spurge” derives from its smaller size compared to other species of the genus Euphorbia. There are no particular folkloric references or documented food uses, precisely because of its toxicity.

Etymology

The genus name Euphorbia derives from the Greek “euphorbion”, a name attributed to a plant used by the physician of Mauretania Euphorbus, from which also the historical root of the scientific name derives. The specific name “peplus” seems to refer to the Greek term “πέπλος” (péplos), meaning “mantle” or “robe”, probably due to the resemblance of the bracts surrounding the inflorescence to a cloak.

The Italian name “Petty Spurge” refers to the relatively small size compared to other similar euphorbias.

Sources

• Prof. P.V. Arrigoni, "Flora analitica della Toscana", "Flora dell'Isola di Sardegna"
• 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)