Emilie Justen and Monika Chandler, Minnesota Department of Agriculture
March’s Weed of the Month, leafy spurge (Euphorbia esula) is an invader of pastures, forage, grasslands, and ditches. It is native to Eurasia and has become widespread throughout the United States. Leafy spurge was introduced to Minnesota in 1890 with a bushel of oats from Russia. By 1992, it was estimated that there were 800,000 infested acres in the central, northern, and western parts of the state, in addition to the Twin Cities area. In response, approximately nine million leafy spurge beetles (Aphthona lacertosa) were released at over 2,000 sites in Minnesota from 1994 to present as a biological control. Biological control with the beetles has been overwhelmingly cost-effective and successful at greatly reducing infestations at most sites. The use of beetles to control spurge continues to be a collaborative effort with public and private land managers, County Agricultural Inspectors and the Minnesota Department of Agriculture (MDA).
Leafy spurge is an herbaceous perennial that grows up to four feet tall. The leaves and flowers of leafy spurge are distinctive. The leaves are linear, simple and blue-green in color. The small, greenish-yellow flowers bloom in May-June in clusters at the ends of the stems and do not have petals. Instead, the plant develops yellowish bracts just below the flowers that give the appearance of petals. After flowering, leafy spurge produces seed that can be expelled up to 20 feet away from the plant. Each plant can produce large clumps of shoots from extensive underground stems and roots allowing the weed to overtake other vegetation quickly. When the shoot is broken, it exudes a milky sap that can cause skin irritation. The sap is also toxic to cattle and horses.
Once a stand of leafy spurge becomes established and spreads, it reduces pasture or grassland productivity. If leafy spurge is present in a hayfield, the hay cannot be cut and moved resulting in economic loss. Infestations can displace native plants and reduce wildlife habitat.
Leafy spurge grows in a wide range of habitats. In addition to pastures, grasslands and ditches, it infests disturbed habitats. It tolerates dry soil in full sun to moist, rich soils. The plant can spread vegetatively by root pieces and lateral roots, making it difficult to control. It also produces a deep and extensive root system that allows it to recover after mowing or spraying.
As a prohibited noxious weed on the control list, landowners must attempt to control the spread of propagating parts by preventing the seed from maturing. To manage leafy spurge, infestations need to be monitored and treated until the seedbanks and resprouts are depleted.