Ageratina Species, Croftonweed, Sticky Snakeroot, Thoroughwort

U. S. FEDERALLY LISTED NOXIOUS WEED.
Not allowed for import to the US and not allowed in any interstate or intrastate transportat...Read Moreion without a specific permit from USDA APHIS PPQ (Plant Protection and Quarantine).

This plant escaped cultivation, and has become an invasive weed problem. It disperses thousands of seeds, which will quickly establish i...Read Moren any bare area. It requires light to germinate, but once established, it will tolerate a fair amount of shade. Often confused for its close relative, Ageratina riparia (Mistflower), the flowers are very similar, but the plants can be distinguished by their habit - A. adenophora is taller and upright, while A. riparia sprawls, reaching a maximum height of 1 ft/30 cm. Their leaves are also different, Croftonweed having broad-toothed leaves (vs. narrow, elongated toothed leaves of Mistflower.)