Introduced from Europe leafy spurge is an invasive noxious weed that grows in a wide range of habitats, including roadsides, banks of rivers and irrigation ditches, pastures and prairies.
Cattle and horses rarely eat the plant unless starving. Sheep and goats however will eat leafy spurge readily with minimal problem.
Leafy spurge invading pasture
Diterpene esters in the milky sap are strong irritants causing blistering of the skin in some humans that handle the plants. Salivation, vomiting and diarrhea may result from irritation to the digestive tract.
A prolific perennial, up to 3 feet tall, reproducing by seeds and an extensive root system. Leaves are alternate, narrow, 1-4 inches long. Multiple stems arise from the root crowns. The plant contains a milky sap in the stems and leaves. Flowers are very small, yellowish-green, and arranged in terminal clusters. Conspicuous yellowish-green heart-shaped bracts surround each flower. Seed capsules explode when dry, scattering seeds.
Leafy spurge is a member of a very large family of plants with at least 2000 species. There is wide variety in the genus, but all spurges contain a milky sap in the stems and leaves.
Excessive salivation, vomiting, colic and diarrhea may occur in animals other than sheep eating leafy spurge. Sheep will loose weight if on a diet exclusively consisting of leafy spurge. Leafy spurge does not provide a nutritious diet by itself.
Sheep fed diets consisting of 100% leafy spurge loose weight because of its poor nutritive value
Once removed from the spurge animals recover uneventfully.
Reddening, swelling and blistering of the skin may occurr in some people handling the milky sap of leafy spurge. Some species of spurge (Euphorbia myrsinites - creeping spurge) appears to be especially irriating to human skin.
The sap can cause severe eye irritation
THe greatest significance of leafy spurge is that it is highly invasive, very difficult to erradicate and therefore displaces good forages and grasses thereby decreasing the value of the land for livestock grazing.
Sheep and goats can be used as effective biological controls of leafy spurge. However, if sheep are grazing the plant when seeds are present, about 20% of te seeds remain viable after passing through the digetsive tract. Before moving sheep to a clean pasture, they should be held 4-5 days in a coral to allow passage of all viable seeds from their digestive tract.
The use of specific leafy spurge beetles that feed exclusively on the plant has shown good promise as a biological control.
Honey from bees feeding extensively on leafy spurge is reportedly bitter due to the presence of diterpenoids.