Wolf's Milk Euphorbia esula

Leafy spurge is a perennial wildflower with a prolific growth rate that often grows in thick clumps. This plant is native from the Azores to temperate Eurasia and is typically found in waste places, roadsides, and dry soil. Leafy spurge tends to displace native grasses and most other vegetation in pastures, rangelands and natural areas in some areas of the United States. Its roots reach down 15 feet or more, and once established it is very difficult to control. It spreads both underground and by seed. Its cultivation is prohibited in ten US states and is declared a noxious weed in twelve others. This plant was accidentally introduced into the United States in the 1800's as a seed contaminate. It is a member of the spurge family (Euphorbiaceae).

Leafy spurge prefers full sunlight and dry soil but can tolerate a variety of habitats. Its roots grow twice as fast in sandy soil as in clay soil; however, the roots in clay soil have greater branching than those in sandy soil. It is especially aggressive in semi-arid situations.

The leafy spurge root system can be large and persistent. The taproots can extend 15 feet deep and spread up to 35 feet. The stems are erect, smooth, and branch at the top. Although herbaceous, it has a woody stem that, when open, can ooze a toxic milky sap.The leaves are smooth and lance-shaped on the lower stem, but they are ovate closer to the flower. The flowers grow from the leaf axil and are small clusters at the top of each stem and have yellowish-green bracts. Blooming occurs from June to fall. The fruit is a 3-lobed green capsule and contains pale to dark brown or yellow-brown seeds. The seed capsules dehisce or "explode," and  the seeds are then propelled up to 15 to 20 feet.

Leafy spurge has the most extensive infestations in the northern Rocky Mountains and the Great Plain states of the US. In the eastern United States, the plant is classified as a weed found in pastures and roadsides.

Diseases, Insects, and Other Plant Problems: No known diseases or insect problems.

Leafy spurge spreads quickly. In the western and northern states of the United States. It is considered invasive and a noxious weed. The World Conservation Union (IUCN) has placed this species on its list of 100 of the world's worst invasive species. To control a small are of these plants, hand pulling or digging is recommended, providing the root system is removed. If needed, several biological or chemical agents are available. Herbicides are effective way to manage leafy spurge infestations.

Wear protective gloves when handling this plant due to possible skin or eye irritation from its toxic sap. All parts of this plant are toxic if ingested. Monitor pets and small children.

VIDEO Created by Laura Barth for "Houseplants, Succulents, and Cacti," a plant identification course offered in partnership with Longwood Gardens.

More information on Euphorbia.