Eggleaf Spurge (Euphorbia
oblongata Griseb.) Family: Euphorbiaceae Description and VariationDescription and Variation: Euphorbia oblongata is a perennial herb, reaching to about three feet tall, from a woody rootstock. Several stems, often hairy when young, arise from a central crown. The leaf arrangement is alternate. The oblong leaves are glabrous (smooth and hairless) with finely toothed margins. Eggleaf spurge is monoecious, with male and female flowers on the same plant. The inflorescence is a cyathium, found in clusters. The glandular bracts below the cyathium are yellow, ovate, and rounded at the base. The whorl of leaves below the flowers are yellowish and oblong and they appear in May, depending on the site. The fruit is a three-lobed capsule. The seed is olive-brown, smooth and shiny. (Hickman 1993; Turner 1995). Economic ImportanceEconomic Importance: Detrimental: Eggleaf spurge is closely related to and exhibits invasive and competitive strategies similar to leafy spurge (E. esula). This ornamental species escaped cultivation, and is located in a natural area in San Juan County. The heavy root is very difficult to remove, and new shoots are consistently present on follow-up monitoring. Eggleaf spurge also has a white latex sap common to Euphorbia, and contact should be avoided. Beneficial: Eggleaf spurge is sold as a garden ornamental and is very drought tolerant. (Heronswood Nursery). HabitatHabitat: In its native range, eggleaf spurge is found in damp meadows, shady woodlands or waste areas, and also in dry hillsides (Turner 1995). In Washington, this species is found on a very dry hillside with a southern exposure, in an open and very sandy and rocky Mediterranean type of soil, growing under blackberry bushes. (Personal conversation with San Juan Co. Coordinator). Geographic Distribution: Eggleaf spurge is native to Macedonia, Albania, the Aegean Islands, Western Turkey, and Greece and is found at elevations from 650 - 2600 ft. (Turner 1995). HistoryHistory: The request for identification for this species came from the San Juan County Coordinator, in May, 1998. Two sites were located on San Juan Island, Washington. The original site is estimated as 30 by 40 feet. The second site originated as an ornamental planting. This has spread and is proving to be very difficult to control. (Lee 1998 correspondence). Previously not known to Washington state, eggleaf spurge is considered a noxious weed in California and often found in waste places (Hickman 1993). Growth and DevelopmentGrowth and Development: Eggleaf spurge is a perennial plant that grows from a central crown with a woody rootstock. The stems die back annually. The yellow bracts appear in May. When mechanically cut after flower production, eggleaf spurge will produce a new set of flowering shoots (Turner 1995). ReproductionReproduction: Eggleaf spurge spreads by seed or division. Response to HerbicidesResponse to Herbicides: None known. Response to Cultural MethodsResponse to Cultural Methods: None known. Response to Mechanical MethodsResponse to Mechanical Methods: When mechanically cut after flower production, eggleaf spurge will produce a new set of flowering shoots (Turner 1995). Pulling is not a control option. Because of the large tap root, it must be dug out for effective control (Personal conversation with San Juan County coordinator). Biocontrol PotentialsBiocontrol Potentials: None known. Rationale for Listing: Euphorbia oblongata meets the requirements for a Class A noxious weed. This species has a limited distribution, it escaped cultivation, and is considered invasive, competitive, and difficult to control in natural areas. Hand-digging to remove the woody rootstock is an effective control option, at this time, while the infestation is still small. The very limited distribution of this plant makes it feasible to eradicate E. oblongata in Washington state. Eggleaf spurge is closely related to leafy spurge (E. esula). Leafy spurge is considered to have the highest priority for prevention, control, and containment by the Washington State Noxious Weed Control Board because of its ability to invade and dominate a site once established, and because of its invasive reputation and history in nearby states. References: *Heronswood Nursery Plant List. 1998. Internet site *Hickman, J. C. 1993. The Jepson Manual Higher Plants of California. University of California Press. pp. 573-4. *Lee, R. S. May 27, 1998. Correspondence to the Washington State Noxious Weed Control Board. *Lee, R. S. July 14, 1998. Correspondence to the Washington State Noxious Weed Control Board. *Turner, R. 1995. Euphorbias A Gardeners’ Guide. Timber Press. Portland, OR.
This page was last updated 03/31/07 |
