Information Last Reviewed June 2007
Family: Euphorbiaceae
Symbol: EUES
Home Range/U.S. Introduction:
This species is a native of Eurasia. The first record of its presence in North America was in Massachusetts in 1827. By the early 1900s, plants were in the Western U.S. and Canada.
There are many species of Euphorbia in North America. Diagnostic characters are found in the number and shape of the glands or appendages of the involucre, the number of staminate flowers in the cyathium and the structure of the seed. Most of these are scarcely observable under 10x magnification. If specific delineation of members of this genus is desired, it would be best to consult a regional manual for help.
U.S. Range Map:
Species Description:
Plants are perennial from a deep root with slender creeping rootstocks. The stem is glabrous, containing milky acrid juice, usually with numerous alternate flowering branches below the umbel. The leaves are alternate, broadly linear to narrowly lanceolate-oblong, 3-7 cm long, <1 cm wide, essentially 1-nerved, apices obtuse to mucronate. The leaves subtending the umbel are shorter and broader, lanceolate to ovate. The umbel is comprised of 7 or more rays subtended by a whorl of leaves. The inflorescence is termed a cyathium but appears as a single flower with an involucre resembling a calyx or corolla with united lobes. The involucre has 1-5 nectar-bearing glands on its margin; these are strongly 2-horned. There are greenish-yellow petal-like appendages from beneath the glands. The capsule is warty, ca. 5 mm high; seeds are smooth, round-obovoid, 2 mm long.
Growth Characteristics:
It is reported that the roots of this species may be up to 5 m deep. It is widely spread in grazing lands. Plants reproduce by rhizomes and seeds which, when ripe, are dispersed up to 5 m from the parent plants. It is believed that water and animals also disperse the seeds.
Problems:
This species tends to outcompete other species. It is reported to occupy more than 1 million ha of land. The plants contain a milky juice that is an irritant to some animals.