Leafy spurge, a member of the Spurge family, was introduced from Europe. It is a creeping perennial which reproduces by seed and extensive creeping roots. The roots extend as deep as 30 feet and are extremely wide-spreading. The shoots grow erect, one to three feet high, are pale green and unbranched except for flower clusters.
Leaves are alternate, narrowly linear with smooth margins, about ¼ inch wide, and one to four inches long. The small yellow-green flowers are enclosed by a pair of yellowish-green, heart shaped bracts. The bracts have the appearance of flowers. The pods are three-seeded. The plant, including the root, has a milky latex that is damaging to eyes and sensitive skin.
Leafy spurge is an extremely difficult plant to control because of its extensive sprouting root system and is probably the most serious noxious weed threat in Colorado. It is adapted to a wide variety of habitats in the state and is very competitive with other plant species. If it becomes established in range-land, pasture, and riparian sites, it may exclude all other vegetation due to its competitive nature. Although it is unpalatable to cattle, sheep and goats eat spurge, do well on it, and are useful biocontrol tools.
For more info and how to control, check out the La Plata County Weeds Dept. Fact Sheet