Knotweed Eradication October 5, 2005 What’s green, comes from the other side of the world, and is taking over our streambanks? Why, Japanese knotweed, of course! You may know this plant by its tall, bamboo-like stalks, broad, leathery leaves, and late-summer sprays of lovely yellow-white flowers. Japanese knotweed (Polygonum cuspidatum) was brought from Japan to the UK as a prize-winning addition to Kew Gardens, then on to the US around 1900. Used as an ornamental plant, it was thought that knotweed could also help control erosion. Unfortunately for our native plants, knotweed has become a growing problem (pun intended!) over the years, proving to be far more of a contributor to erosion than a solution. The Black River Action Team has an exciting opportunity to help manage this vegetative invader. Read on! The plant’s shoots grow early and very quickly, usually in areas disturbed by erosion or excavation. For a plant whose native habitat is the slopes of a volcano, it’s not a challenge to take hold in New England. In fact, knotweed is a recognized problem in almost every state, including Alaska! Its root system consists of a softball-sized rhizome with finger-like roots that can extend some 20-60 feet from the rhizome, before emerging in late April. The young shoots look similar to asparagus and are edible when less than six inches tall. They rapidly form dense stands of hard, green, jointed stalks with broad, tough leaves. These stands increase in size each year; in the US, knotweed spreads primarily by vegetative means. Whenever a piece breaks off, it starts a whole new colony ~ even a chunk the size of a macaroni elbow! Knotweed has many ways to travel: floating downstream, being transported from one part of a river to another by human cutting or mowing, flooding, even beaver activity; it can hitch a ride on equipment being used at construction sites or roadside mowing. Even pieces that snap off in the natural course of events can start a whole new life somewhere else. There is mounting evidence that knotweed poses a real threat to streambanks, and the quality of water in our rivers ~ this can have serious consequences for habitat both in the water and along the banks. By out-competing other plant species for light, soil nutrients and space, knotweed forms massive monocultures (dense stands of only one species of plant), even crowding out trees. Each fall, as the leaves and stalks die, they remain on the ground, stifling the growth of anything else and taking two years or more to decompose. There is little to forage for in the leaf litter, and the leaves are not eaten by any wild herbivores that have been documented, although pigs and goats have been known to chow down on the stuff! Just don’t let them clear a streambank and cause more erosion problems. When the heavy spring rains come, the round root-ball does very little to stop the soil from washing away into the river; imagine you are holding a fine-mesh butterfly net (the root system of many native trees and plants) in one hand, and have the other with simply an open palm. It’s pretty obvious which better will hold a pound of thick mud! A first step in getting a handle on this problem is to know where knotweed is in our watershed. Two years ago, the BRAT conducted a Visual Assessment on the Black River, and we’re HOPING to do something similar again. In partnership with the Southern Windsor County Regional Planning Commission (SWCRPC), the Ottauquechee Natural Resources Conservation District (ONRCD), and the state of Vermont watershed coordinator, the BRAT is applying for a grant to use the Visual Assessment techniques and maps to visually locate stands of knotweed. If the grant is successful, this mapping will take place in Summer of 2007. There will be simple training provided (so you know what to look for and how to record it), as well as any materials you might need. Since knotweed often travels downstream with the water, we’ll need to start in the upper-most reaches of the watershed first, in the Plymouth, VT area, targeting the tributaries specifically. Our basic information will be hand-recorded on maps, and the SWCRPC will then take GPS readings of the locations we have noted. Once there is a solid bank of data on knotweed infestations in the tributaries of the Black River, Phase II can begin: control. In addition to the mapping and the control (a combination of cutting & covering techniques and herbicide treatment), we also plan to have some demonstration sites set up in places like Springfield and Ludlow, to show folks what knotweed is and to illustrate the different control techniques. As you might expect, there will be a heavy emphasis on working cooperatively with landowners, helping folks get the information they need about knotweed on their property, as well as about how to control and manage it effectively. This is in the planning stages at the moment, but I’m working to get as much feedback from you as possible. If you have any interest in learning more about knotweed, or in participating with the BRAT and the other partners on this terrific project, please let me know ASAP. We hope the mapping will take place next summer, with informational meetings and demonstration sites along the way. Thank you! And cross your fingers that we get the grant! Kelly |
