Weed Wisdom Nov. 2020
Leafy Spurge (Euphorbia esula L.)
By: Kasey Dunn and Charles Geddes
Leafy spurge (Euphorbia esula L.) is a perennial weed species introduced to North America in the early 1800s. The first plant was discovered in Alberta in 1933. It can reproduce by seed, but its persistence is mainly due to vegetative reproduction by a vastly extensive creeping root system.
Leafy spurge roots can extend up to 4.5m laterally and approximately 9m in depth. It can form very dense stands over time and a large plant can produce up to 130,000 seeds. All parts of the plant contain a milky coloured latex that can poison livestock and cause severe skin irritations to humans. Leafy spurge is classified as a noxious weed in Alberta with increased biological control applications implemented in the province in recent years.
As a species that is extremely difficult to eradicate, Leafy spurge makes it difficult to grow crops in infected areas. Germination and growth of other plants can be inhibited by allelochemicals produced by Leafy spurge, especially from the roots. The milky sap it excretes can coat farm equipment and legs of livestock and is very difficult to remove. It can cause severe blistering and loss of hair on horses’ feet and, as mentioned, blistering and dermatitis in humans. Reports say that leafy spurge can cause scours and weakness in cattle, but normally livestock do not consume Leafy spurge unless no other feed is available.
Native to Europe and Asia, Leafy spurge adapted to a very wide range of habitats including pastures, rangelands, meadows, roadsides, railroads and waste areas. It is widespread throughout Alberta and grows in a variety of soil types. It can tolerate very wet to very dry climates and seasonal flooding of riparian populations can distribute seed over long distances.
Special identifying features of Leafy spurge include an erect herbaceous perennial, and simple unbranched stems. Mostly smooth and hairless, it can grow up to 1 m tall. The leaves are numerous and attached directly to the stem in an alternate or sometimes spiraling arrangement. The inflorescence is a terminal umbel. Flowers are small and yellow, and lack petals and sepals, but are supported by two bright green heart shaped bracts. Seeds are light gray to brown, numerous, about 2mm in diameter and grow in pods at top of the bracts.
Leafy spurge is resilient, and takes an integrated combination of methods to successfully control infestations. One method of control throughout Alberta is grazing by sheep and goats. In the south, the cities of Lethbridge and Medicine Hat both implemented grazing by goats to control leafy spurge with relative success. The goat’s systems are unaffected by the toxins within Leafy spurge and re-sprouting of the stems will be stunted by this method. However there is still a risk of seed being carried by the animals.
Intensive growing season, as well as fall-only, cultivation programs may help. Hand-pulling and mowing is rather ineffective other than on small and young infestations. Be sure to wear gloves and protective clothing and ensure to wash hands thoroughly after handling Leafy spurge to prevent rashes.
Chemical control requires choosing a herbicide that can translocate throughout the plant to control the perennial root system. Consult the Crop Protection Guide (Blue Book) for registered herbicide options.
Best, K.F., Bowes, G.G., Thomas, A.G. and Maw, M.G. 1980. The Biology of Canadian Weeds. 39 Euphorbia esula L. Canadian Journal of Plant Science. 60: 651-663