Resistance to Three Common Herbicides in Chameleon Plant (Houttuynia Cordata Thunb.), a Highly Invasive Exotic Species

Abstract

Chameleon plant (Houttuynia cordata Thunb.) is native to Southern and Southeastern Asia. It can reproduce sexually through seeds and asexually through rhizomes and is invasive in multiple countries including the U.S. There has been much research on H. cordata as a medicinal species, and its potential as an invasive species is well documented. However, its herbicidal resistance has not previously been quantified. The objective of this study is to assess H. cordata’s resistance to herbicides. This study consisted of two rounds of tests to examine the resistance of H. cordata plants to three commonly used herbicides: SpeedZone, Weed-B-Gon, and Roundup. Two concentrations of each herbicide were used during each trial in the study: the recommended concentration and twice the recommended concentration. Herbicide treatments were applied outside the greenhouse. Herbicides were sprayed uniformly on the plants until the herbicide was dripping off the leaves. The growth of the treated plants was then monitored in the greenhouse. The herbicides generally reduced growth of the plants temporarily. However, plant extermination was not achieved. Plant samples from all herbicidal treatments regrew from rhizomes after all herbicide treatments. Results from the study showed that H. cordata could not be controlled by the recommended concentrations of herbicides commercially available for horticultural uses in the U.S. Doubling the recommended herbicide concentration was also ineffective in exterminating H. cordata plants. This research clearly showed that H. cordata has the potential to become a highly invasive species with the potential to negatively affect the ecological integrity of many communities in the U.S.