Boise National Forest is directed by the U.S. Forest Service to " control the establishment , spread , or invasion of non @-@ indigenous plant species in otherwise healthy native vegetative ecosystems . " The forest 's plan address the need to control invasive plants , and management efforts include chemical , mechanical , and biological control methods . Invasive plants that are of particular concern in Boise National Forest include spotted knapweed , yellow star @-@ thistle , rush skeletonweed , and leafy spurge , among others .