Weeds of Container Nurseries in the United States

Horseweed is a winter annual in the aster family. Peak germination is in late autumn and early spring but sporadic germination may occur anytime except summer. It forms a rosette of hairy leaves. In spring, plants bolt upright 3 to 6 feet tall. Individual flowers are small, with white ray flowers and yellow disk flowers. Seeds are spread by wind. Do not let plants go to seed in the nursery. Control horseweed around the property to prevent spread. When hand weeding, remove completely as plants can re-sprout from broken stems. Horseweed can be controlled by preemergence broadleaf herbicides labeled for nursery use. Note: glyphosate-resistant horseweed has been reported in areas where glyphosate-resistant crops are grown. Wind-dispersed seed are likely to spread from those areas.