Leafy spurge, a native of Eurasia, was introduced to the United States in the 1800’s through soil ballast and contaminated seed imported from Russia. It now occurs in at least 26 states and six Canadian provinces. In Washington, leafy spurge has been found in 18 counties, both east and west of the Cascade Mountains. The largest infestations are in the northeastern part of the state. Leafy spurge is a Class B noxious weed in Washington. Control (prevention of all seed production) is required in designated areas.

Leafy spurge is an extremely aggressive plant. Once established, it tends to displace all other vegetation in pastures, rangeland, and natural areas, forming single-species stands. Infestations can reduce yields of desirable species by 10 to 100 percent. These losses have devastating economic consequences. In North Dakota, where leafy spurge covers over 1 million acres, the total annual economic impact has been estimated at $87 million. In the Pacific Northwest, spurge-infested ranches have sold for as little as ten percent of their original value.

Leafy spurge also has toxic properties. Although it is generally avoided by grazing animals, when ingested, it may cause severe lesions in the mouth, weakness, and sometimes death. Leafy spurge is also a human health hazard. The plant produces a white latex, which can cause severe dermatitis in humans and animals. Upon eye contact, the latex may even cause human blindness. In addition, the latex has co-carcinogenic factors, which increase the cancer-causing properties of other substances.

This perennial plant grows from semi-woody root crowns. Mature leafy spurge plants have extensive roots systems that may extend 15 or more feet into the soil. Many plants also have horizontal roots that allow them to expand vegetatively.

Other spurge species are sometimes confused with leafy spurge. These species share leafy spurge’s white latex and toxic properties. Cypress spurge (Euphorbia cyparissias) is one of several closely related species that can hybridize with leafy spurge. It can be recognized by its densely leafy lateral branches, and its leaves, which are narrower than leafy spurge leaves. It is considered a noxious weed in some states and provinces. Petty spurge (Euphorbia peplus), another weedy relative, is a common garden pest. An annual plant, petty spurge lacks leafy spurge’s extensive root system. Several spurges are planted as ornamentals and may escape cultivation. Caper spurge or mole plant (Euphorbia lathyrus) is sometimes planted to repel moles and gophers. Unlike related spurges, which have alternate leaves, caper spurge’s lower leaves occur opposite each other along the stem, and each leaf pair occurs at right angles to the pair above and below it. Myrtle spurge (Euphorbia myrsinites), another ornamental, has bluish-white leaves and stems that trail along the ground.

The plant spreads by seed and root. Mature leafy spurge fruits explode, sending seeds out up to 15 feet. The seeds may be transported by water or animals. Leafy spurge also spreads via roots. The root system is deep and spreading. Shoot buds can be produced at almost any point along any root segment. Even if the upper portion of the plant is killed, remaining roots can send up new shoots. However, most long distance dispersal can be attributed to human activities. Leafy spurge is transported as a contaminant in seed, feed grain, and forages.

Control of well-established infestations always requires a carefully planned and integrated approach. Sheep and goats will graze leafy spurge preferentially without ill effect to the animals. Grazing will suppress leafy spurge, but the animals must be carefully managed. Establishing competitive vegetation, in combination with the use of certain selective herbicides can be effective. Contact your local county noxious weed control board, weed district, or Washington State University Cooperative Extension offices for assistance developing control strategies for specific sites.

Comparison of Selected Spurge Species

By Lisa E. Lantz, M.S., Washington State Noxious Weed Control Board Executive Secretary.

   This page last updated 03/31/07