Euphorbia terracina

Name and classification

Euphorbia terracina L.
(=Euphorbia halacsyi Formánek; Tithymalus terracina (L.) Klotzsch & Garcke)
Family Euphorbiaceae

Common names

false caper

Disseminule

seed

Description

Fruit a strongly trilobate and explosively dehiscent capsule, with one seed in each of the three chambers. Capsule 3–4 mm long, 4–5 mm diameter, smooth. Seeds broadly ovate to broadly oblong, subterete, 2.0–3.0 mm long, 1.5–2.0 mm in diameter; base of seed flat, oblique, with hilum usually obscured by persistent cartilaginous caruncle. Caruncle boat-shaped, up to 1.5 mm long, mildly sparkly, cream-colored, stalked, appressed obliquely to testa. Raphe a prominent dark line extending longitudinally from the hilum to the chalazal area at the apex. Chalaza prominent, round, depressed, 0.7 mm across. Testa minutely pitted and appearing smooth, greyish-white to bluish-grey to tan, and usually mottled or flecked with brown or black markings. Hilum darker than testa, grading into raphe. Embryo spatulate; endosperm readily visible.

Identification considerations

Similar species

Euphorbia esula L.

Euphorbia lucida Waldst. & Kit. (non-FNW)

Distribution

native to African, Asian, and European countries surrounding the Mediterranean Sea

introduced to Mexico, Australia, and California, United States

Habitat

rocky limestone slopes, sandy beaches and dunes; also common along roadsides, often on shallow soils with high calcium carbonate content

General information

Euphorbia terracina is a deep-rooted perennial herb, up to 80 cm tall. Rapid growth and prolific seeding enable this species to form dense thickets. It is an aggressive weed, but does not persist on frequenly cultivated soil. Dispersal can be by water, muddy animal feet, machinery and various human activities. Toxic to stock.

seeds, some with caruncle still attached

seeds, some with caruncle still attached

seed, detail

seed, detail

A–B, seed in two views; C, embryo in situ; D, transection of seed; drawing by Lynda E. Chandler

A–B, seed in two views; C, embryo in situ; D, transection of seed; drawing by Lynda E. Chandler

chalaza of seed

chalaza of seed

hilum of seed

hilum of seed

caruncle of seed

caruncle of seed

fruit

fruit