[Wikipedia] Europe & Asia native, invasiveness: Euphorbia virgata, commonly known as leafy spurge, wolf's milk leafy spurge, or wolf's milk is a species of spurge native to Europe and Asia, and introduced in North America, where it is an invasive species. Leafy spurge was transported to the United States possibly as a seed impurity in the early 19th century. It now occurs across much of the northern U.S., with the most extensive infestations reported for Montana, North Dakota, Nebraska, South Dakota, and Wyoming. Since the introduction of leafy spurge to the United States, it has been found in 458 counties in 26 states.[2] It has been identified as a serious weed on a number of national parks and on reserves of The Nature Conservancy in eleven northern states. It is now classified as an invasive species by the United States Department of Agriculture. (link added by Mary Ann Machi)