Arriving in North America in the 1800s as an accidental seed contaminant from Eurasia, leafy spurge has become one of the continent's most studied and most persistent invasive plants. It forms thick clumps topped with yellowish-green bracts from June through fall, and its taproot system can reach 15 feet deep and spread laterally up to 35 feet, making established colonies extraordinarily difficult to eliminate. It has displaced native grasses and wildflowers across pastures, rangelands, and natural areas throughout the northern Rockies and Great Plains.

Its cultivation is prohibited in ten US states and it appears on the World Conservation Union's list of the 100 worst invasive species. Where small infestations exist, hand removal with full root extraction is recommended; larger areas require herbicides or approved biological controls. The stems exude a toxic milky sap on contact. This entry exists as a reference for those who encounter it in the landscape and need to identify what they are dealing with.