With roots that can run 10 feet deep and a zombie-like afterlife, knotweed is a difficult invasive to control.
Several invasive plants are growing strong in our region right now, including Japanese knotweed.
A native plant from Japan, this edible is consumed as a leafy green when it first sprouts. And in Japan, several insects and fungal diseases keep knotweed from growing out of control there.
Here in Vermont, as well as elsewhere in the U.S. and the world, knotweed has no natural controls so it grows indiscriminately.
This kind of prolific growing pattern can crowd out all kinds of native plants and reduces biodiversity.
In Vermont right about now, you may be seeing Japanese knotweed taking over streambanks and wetland areas, which is where it thrives best. If you're curious to see if this invasive plant is on your property, you'll know Japanese knotweed by its tell-tale red shoots and almost shovel- or heart-shaped leaves.
The plant also flowers and produces petals that are a creamy white color. Another way to know if what you're seeing is true knotweed is to snap off one of the canes. If the stems are hollow, it's knotweed.
And this invasive plant is a tough one to control. Japanese knotweed has a massive underground root system known as a rhizome. These roots are resilient. They can overwinter. They can survive being pulled up and regrow after being chopped. And they can run up to 20 feet horizontally and even 10 feet down into your soil.
In addition to the super-strong root system, knotweed also spreads from seed. If you have Japanese knotweed on your property and want to remove it, the first step is to be realistic. Eradicating it may take years of diligence!
Next, place all the knotweed in black plastic bags and leave the bags outside for a number of weeks. Don't dispose of leaves, stems or roots in your compost; you will just grow even more knotweed!
Cover the area where you've removed the knotweed with a thick plastic tarp and keep the tarp in place by holding it down with heavy stones or boards. And then, wait.
A year from now, remove that tarp. You will see some knotweed sprouts coming up, but they will have weakened. Wait till after a good rain, then go into the area and dig out the new sprouts. And keep up the practice for a number of years. Slowly, your diligence will be rewarded and you will have rid your lawn or field of the knotweed.
If you're not near water and you're inclined to use it, you can try a chemical herbicide. To use herbicide, you'll need to cut the stalks of the knotweed plants down to about six inches tall. And if having to repeatedly cut back the resilient weed only to watch it grow back again wasn't zombie-like enough, you'll need a foam injector for this next bit.
Using an injector, flood the herbicide into the knotweed stems. This will kill the plant by attacking the root system. Again, it won't completely do in the robust rhizome system. You'll have to come back the next year and dig out any new sprouting leaves.
Or you could always eat it! The internet is full of ways to harvest and cook Japanese knotweed.
Q: Our house had this giant holly tree when we bought it. The birds love it and the bees swarm there in May, but the leaves are sharp! Time in the garden usually results in some profanity, even with gloves on! And if I cut this thing way down, would it be possible to bush out? Or will it always be this weird single trunk form? I'd like to make it more manageable and keep it for the birds and bees. - Leslie, in Boston, MA
A: Luckily, an evergreen holly can, indeed, be cut way down. In fact, if you want to cut it to three or four feet, that's fine to do.You can do it now or you can wait till late winter or even spring to do it. Cut it way back and it will regrow. And then, as it grows, you can train into the shape and size that you want.
Q: My first year growing potatoes and my potato leaves are turning brown on the edges. And then the leaves slowly die and the whole plant just seems to fade away. Should I pull the affected plants and perhaps I can keep it from spreading up the row? - Anne Marie
A: Your potato plant issue could be due to a number of foliar diseases.If you're not seeing spots and the plants aren't dying back quickly, that could rule out late blight, which is a big concern with potatoes. It might be early blight or another foliar disease, though.
Try pulling up a few of the affected plants. It's late enough in the growing season that you may have some small potatoes under there. Check them for insects or disease and if the spuds look okay, clean them up and enjoy them.
Other than that, leave the healthy-looking plants to continue to grow, then mulch the rest of the potato bed. You'll want to cover the area where the plants that you pulled up were. Use straw, chopped leaves or grass clippings as mulch. This should slow down whatever is affecting your potatoes.
Then think ahead to next year. Rotate your crops, find a new spot, and maybe try a couple of different potato varieties. As for this year, by pulling out the affected plants and mulching, hopefully you'll still be able to get some nice potatoes out of this year's crop, too.
Do you live in the Chittenden County area and keep a veggie or flower garden? How strong is your internet connection? We ask, because we're venturing out to film a live version of All Things Gardening with Charlie Nardozzi! Contact us here and we can share more details about the project.
You can also leave a voicemail with your gardening question by calling Vermont Public at 1-800-639-2192.
Hear All Things Gardening during Weekend Edition Sunday with Vermont Public host Mary Engisch, Sunday mornings at 9:35.