Attack of the Alien Invaders, National Geographic Magazine: Non-Native Sheep Limit Invasive Plant

Sheep chomp through a field of yellow-flowered leafy spurge in North Dakota, where ranchers attempt to control the plants’ spread by moving a flock into a field to mow it to the ground. Leafy spurge made the listing of the world’s top 100 worst invasive aliens as a noxious weed that infests more than five million acres in the U.S and Canada. It drastically reduces rangeland productivity, native plant diversity, wildlife habitat, and land values.

Native to Europe and western Asia, leafy spurge (Euphorbia esula), was introduced into the western U.S as a seed contaminate in the late 1800s.

The Eurasian weed contains latex, is poisonous to some animals, and causes burning sensations in the mouth for cattle and cows. Sheep, however, flock to eat leafy spurge like it’s a salad bar.

It is a woody plant and it’s bright yellow flower brackets appear in the spring. Its roots can reach depths up to 15 feet with a lateral spread of up to 35 feet. Seed capsules open explosively, dispersing seeds up to 15 feet which can then live in the soil at least seven years. Even if the foliage is destroyed, the roots will regenerate new shoots. Herbicide and biological controls show some results at curbing the plant.

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