Scoping the Allelopathic Potential of Elsholtzia strobilifera for Managing Himalayan Knotweed Koenigia polystachya, an Invasive Species in Alpine Ecosystems

The increasing intrusion of weed species into alpine regions is an alarming threat to native floras because their strong and deep root systems cause a scarcity of nutrients to native alpine plant species. Considering the sensitive nature of alpine ecosystems, integrated weed management may be a means of preventing invasive species from going out of control. The present study investigated the allelopathic effect of Elsholtzia strobilifera on the germination and growth characteristics of Himalayan knotweed (Koenigia polystachya, syn. Polygonum polystachyum) under both field and laboratory conditions. The germination of seeds under laboratory conditions was studied by using different dilutions of hydrosol and aqueous extracts derived from E. strobilifera. In our field study, seedlings of K. polystachya were planted together with E. strobilifera in their natural habitat at a nursery. The study indicates that the seed germination and morphological parameters of seedlings were significantly inhibited by different dilutions of hydrosol and extract (reduction by 83–96% and 62–73%, respectively). In field conditions, significant inhibition in the morphological characteristics of K. polystachya was observed when grown in association with E. strobilifera. The results reveal that E. strobilifera has a significant allelopathic effect on K. polystachya. Based on the results of the present study, it can be concluded that growing plants of E. strobilifera around K. polystachya may be a novel approach to curbing the spread of the latter and suppressing the population of this species in ecologically sensitive alpine or other endangered areas.