Biological control offers a highly promising management tactic for leafy spurge. It has been released in North America for the biological control of leafy spurge. Leafy spurge grows in a variety of different climate environments. Musk thistle, leafy spurge, and tamarisk are all invasive species found at Philmont. Exotic plant species include leafy spurge, Canada thistle and sweet clover. In Saskatchewan, leafy spurge spread on trails used by settlers and traders. If left uncontrolled for a single year, leafy spurge can reinfest rapidly. The transitional grassland ecosystem is seriously threatened by leafy spurge (Euphorbia esula), an introduced weed. Leafy spurge is being developed as a model to answer fundamental questions of weed biology. Leafy spurge ("Euphorbia esula") and Chinese tallow ("Triadica sebifera") are invasive weeds in North America.