Basics of Leafy Spurge

by Roger Sheley, Range Weeds Specialist

Leafy spurge (Euphorbia esula) is a very serious weed that has been reported from every county in Montana.  It is designated a noxious weed, meaning land owners or managers are legally responsible for its control.  If unchecked, this weed quickly displaces native vegetation. Leafy spurge reduces wildlife, livestock production, and, to some degree, recreation.  It has been estimated that the economic impact of leafy spurge in Montana, North Dakota, South Dakota, and Wyoming totals $129 million each year and may cause the loss of 1,433 jobs.

The pale green or blue green stems of leafy spurge are hairless.  Leaves are also hairless and alternate on the stem.  If the stem is injured, a milky latex sap will flow from the injury.  If ingested, this milky latex is a digestive tract irritant to cattle and, if contacted, can cause lesions around the eyes and mouth.  The green flowers of leafy spurge are small and are surrounded by a pair of yellow-green heart-shaped leaves (bracts) that are often mistaken for flowers.  Figure 1 is a close-up photograph of leafy spurge bracts. 

Click on the photos below to view a larger version.  Photos courtesy of MSU Extension Service.
Figure 1. Leafy spurge bracts.	Fig. 2. Leafy spurge in a meadow.	Fig. 3. Leafy spurge

In early spring, growth from rootstock usually begins.  Because of this competitive advantage, leafy spurge is usually one of the first plants to appear on the landscape.  If the plant is growing from seed, the peak period of seed germination is from late May to early June in northern climates.  However, some germination can occur any time adequate moisture is available.  In the absence of competition, seedling roots can penetrate to a depth of three feet and can spread laterally 40 inches in four months.  By the second year, plants are well-established and will begin flowering and producing seed.

No single management practice or treatment will be effective for this weed.  This means that successful management of leafy spurge requires the use of various combinations of management methods.  In order to manage a leafy spurge infestation, an integrated weed management (IWM) plan will provide the most effective program.  IWM includes the prevention of new infestations through regular landscape monitoring for leafy spurge.  If a small patch of leafy spurge is discovered, quick eradication, usually through herbicide use or through hand pulling of seedlings, will be necessary to prevent the plant from spreading and becoming more costly to manage.  If a large patch of leafy spurge is discovered, control efforts must begin immediately.  For best results, herbicide control should be used as part of a systems approach. Picloram applied at one quart per acre with 2,4-D at one quart per acre provides good control during true flowering, approximately two weeks after appearance of the yellow bracts.  Many types of herbicide treatments are available, each reflecting different rates of control during the growing season. 

Sheep and goats can help suppress leafy spurge by increasing the competitiveness of desirable plants through timing of grazing and selective removal of the weed.  When leafy spurge is grazed, plant competition is altered in favor of grass, browse, and other forbs.  Grasses should be grazed when they have produced seedheads or are mature and not during periods of active growth.  Conversely, leafy spurge should be grazed at least twice during the season to prevent flower and seed production.  It must be grazed often enough and at sufficient stocking rates to deplete root reserves over time, reducing leafy spurge competitiveness. Heavy leafy spurge infestations require 4 - 7 sheep per acre and are usually necessary for the first two to four years. They should be grazed to strip the yellow bracts off the plants; this will effectively prevent flowering. After a few years, the spurge will be reduced to a single occasional plant. Grasses should increase dramatically during that period. Cattle can  graze leafy spurge-infested pastures after sheep remove the spurge shoots.

Biological control agents such as insects or plant pathogens, like fungi and bacteria, have been used with some success.  They will never completely eradicate leafy spurge, but they may reduce populations of leafy spurge over a period of years.  The most successful biological control agents are Aphthona flea beetles in Montana. They can be effective in some areas. Contact your local Extension agent or weed district for information on starting a leafy spurge biological control program.

Reseeding rangeland with a mixture of grass and shrub species may provide a more competitive environment than reseeding with any single species. Research has shown that a singe pass revegetation strategy may be the most cost effective. A fall application of 1 quart of picloram at the same time (same procedure) as fall dormant seeding can effectively reestablish desired vegetation in a single pass.  Plant early-germinating species with leafy spurge seedlings for early season moisture and include species that grow late in the season to compete with fall regrowth of leafy spurge.  When one species matures or enters its dormant phase, another should be starting its active growing phase to continue the competition for moisture and nutrients. The species most competitive with leafy spurge are wheatgrass (low precipitation), pubescent wheatgrass (13-16" precipitation), smooth bromegrass (16-20" precipitation) and bluebunch wheatgrass, a native.

Please contact your local county extension agent or weed district supervisor for additional information and to request the publication Leafy Spurge: Biology, Ecology, and Management (EB 134).

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