When many find that they have an invasive species problem they feel that they need herbicides to even have a chance of controlling the invasive. Japanese knotweed may be the worst of the invasives. Japanese knotweed is not only a fast grower and spreader, it is also maddeningly hard to remove mechanically. Its extensive root system can send up new shoots when stalks are cut down. It is also practically impossible to dig the whole root system out. However, controlling knotweed without chemicals is far more realistic than you might think. While mechanical control admittedly takes a good deal of patience, the results speak for themselves. The knotweed cannot put out shoots indefinitely, so you can easily kill it if you are persistent enough. This takes far less work than you think. If you don’t believe me, let me show you how we removed a large, established japanese knotweed patch at the Intervale Center with surprising ease.
Before:
After:
Our Strategy
The first couple of years, 2012 through 2014, we whacked the knotweed each year, but it had little effect. So, we decided to adopt a more effective strategy. The third year, 2015, we spent less than six work hours on the plot. We pulled up the larger knotweed plants and piled them above the ground so that they wouldn't reroot. The next four years, 2016 through 2019, the same technique was used, taking a similar amount of time.
Each year, the technique was done multiple times per summer when the knotweed would resprout. This still took under ten hours each summer because the knotweed would regrow with reduced vigor, making the job increasingly easy as we depleted the plant's energy stores. In 2020, the Intervale Center gained access to more volunteers and could thus spend more time on the plot with their help. During 2020, we spent a total of fourteen work hours digging, pulling, and cutting knotweed throughout the summer. By 2021, the knotweed plants were so small that they did not take very long to remove: we only spent about six work hours total throughout the whole summer. This whole process took less than seven years and could have taken less if we had put more work into the plot each year.
Current Conditions
While the knotweed technically still exists now, it is small and there is very little of it. The knotweed is struggling to compete with the other plants, which are currently many times the height of the knotweed (even its short cousin, smartweed, is taller than it). Many other plants are fully established in what used to be a monocultural stand of pure knotweed. This makes it unlikely that knotweed is ever going to dominate this plot again.
As the knotweed receded and has weakened over time, we have had the opportunity to plant a variety of native plants in the knotweed’s stead such as highbush cranberry, silky dogwood, elm, chokecherry, and basswood.
All of these native plants being introduced makes it harder for knotweed to come back because there is already something growing in its former colony. It is important to plant natives before other non-native invasive plants spread into the plot such as goutweed. Native plants also help native fauna, which have been in decline in recent years. The plot has gone from a knotweed monoculture to an area with more than thirty plant species. This includes rare plants such as wild senna. For more details, look at the census chart of all of the species spotted in the plot.
Your Turn!
There is nothing special about what we did. Admittedly, we were fortunate because our soil is somewhat easy to work with. We sympathize with you who have areas where knotweed is embedded into stones and boulders. You can do it! Dig, pull, and cut the knotweed. Each site presents its own challenges, but with just a bit of extra work, you will also be able to create a diverse, native landscape from a forest of knotweed.
Check out our blog post on eating knotweed, so you can use the knotweed that you pull up:
The partners of Burlington Wildways believe in the “shared stewardship” model where we encourage and invite our community members to take care of the land on which we live. Want to get involved? Check out the website and become a trail steward HERE.
For more questions contact Natural Areas Stewardship Coordinator, Duncan Murdoch at duncan@intervale.org
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