Ageratina riparia, commonly known as Mistflower or Creeping Croftonweed, is a species of flowering plant in the aster family, native to Mexico, Cuba and Jamaica.
Mistflower is a low growing, sprawling perennial herb that grows up to 40x60 cm high. Its stems produce roots at joints that touch the ground. The serrated leaves on average reach 7.5 cm long and 2.5 cm wide and taper at each end. The flowers are white with dense heads at the ends of the branches. Mistflower buds from July until August, with full flowering occurring from August through October. Seeds are black, slender, angular, 2 mm long, with fine white hairs at the tip. They are dispersed by wind and flowing water. Mature plants can produce between 10000 and 100000 seeds per year. Mistflower can be poisonous for mammals to eat.
Mistflower has been introduced to southern Africa, tropical Asia, Australia, New Zealand, the Canary Islands, Madagascar, Mascarenes, Hawaii, and Peru. It is considered an invasive species, choking out native plants in the mountain and cloud forests of Sri Lanka, and in pastures, roadsides, wastelands and bushlands of other places where it has been introduced with often disastrous effects. It has been reported to have caused lung lesions in horses and to have caused the death of many animals due to habitat loss.
Mistflower can be harvested to use as a tanning agent. It is commonly used as an ornamental plant.
The Mist flower smut fungus has been employed with some success against the species. Mistflower can also be controlled with glyphosate 360 at the rate of 0.5 L/100 L or metsulfuron methyl at the rate of 5 g/100 L.