Siam Weed Flower

Chromolaena odorata is a rapidly growing perennial herb. It is a multi-stemmed shrub to 2.5 m (100 inches) tall in open areas. It has soft stems but the base of the shrub is woody. In shady areas it becomes etiolated and behaves as a creeper, growing on other vegetation. It can then become up to 10 m (33 feet) tall. The plant is hairy and glandular and the leaves give off a pungent, aromatic odour when crushed. The leaves are opposite, triangular to elliptical with serrated edges. Leaves are 4–10 cm long by 1–5 cm wide (up to 4 x 2 inches). Leaf petioles are 1–4 cm long. The white to pale pink tubular flowers are in panicles of 10 to 35 flowers that form at the ends of branches. The seeds are achenes and are somewhat hairy. They are mostly spread by the wind, but can also cling to fur, clothes and machinery, enabling long distance dispersal. Seed production is about 80000 to 90000 per plant. Seeds need light to germinate. The plant can regenerate from the roots. In favorable conditions the plant can grow more than 3 cm per day.[7]

Recently C. odorata previously known as Eupatorium odoratum has been implicated in the larvicidal activity of all the major mosquito vectors (Reference: Gade S, Rajamanikyam M, Vadlapudi V, Nukala KM, Aluvala R, Giddigari C, Karanam NJ, Barua NC, Pandey R, Upadhyayula VS, Sripadi P, Amanchy R, Upadhyayula SM. Acetylcholinesterase inhibitory activity of stigmasterol & hexacosanol is responsible for larvicidal and repellent properties of Chromolaena odorata. Biochim Biophys Acta. 2017 Mar;1861(3):541-550.)