Know your enemy well
As a newcomer to the wonderful wilds of New Hampshire, I find some aspects of life here come with a learning curve, and thought I’d share.
Gardening is something I’ve always enjoyed, and maybe I don’t want to keep the neatest yard in the neighborhood, but I want to be able to enjoy it and have things at least look “nice.” This has led me to a confrontation with Polyganum cuspidatum, otherwise known as “bamboo,” but it’s not really bamboo.
Like a nefarious enemy it goes by many names, like Knotweed or Japanese Knotwood. My favorite is Donkey Rhubarb, though it’s not really rhubarb. And in the country of its origin it’s called “Itadori.” Admittedly, it looks like bamboo, and covers many a field, hill and roadside, including the hill in my yard.
You know the stuff — it’s everywhere there’s sun and it grows like nothing I’ve ever seen, except maybe for Kudzu. How fast does it grow? Here are some “fun facts.”
Under ideal conditions Knotweed can grow almost 3 inches per day. The root ball is called a rhizome, and may extend horizontally underground for about 23 feet, and go as far as nine feet down. Ten square feet of root ball can produce 238 raw shoots, and it’s thought the largest stand in Europe covers over 5,400 square feet.
Obviously this is one of several invasive species of plants and animals that has caused havoc when removed from their native habitat and unceremoniously plopped down in a new environment. In fact the British government has practically declared war on the Knotweed. It’s been called Britain’s most invasive plant species and it is illegal to plant it in the wild anywhere in the UK.
The story of how it came to be in my yard begins in the late 1700s when well-meaning Swedish naturalist Carl Peter Thurnburg recorded its discovery. By 1840 a nursery in Leiden, The Netherlands aggressively marketed the plant. Many seemed to think it would make a natural screen for the boarders of properties, and they were right. It sure does grow quickly. So the nursery merrily sent Japanese Knotweed all over Europe. Botanists began to worry around 1887.
It seems the plant was being its aggressive self. It can uproot a driveway. Concrete foundations were being damaged and when the weed dies off in the winter it seemed to weaken defensive flood dikes. It had also started to alter the habitats where it grew. The plant produces shade where other native plants can’t thrive.
By the time warning bells were going off, Knotweed was making its way to North America. Sometime in the late 19th century, enterprising gardeners brought it “across the pond.”
It’s estimated about $500 million is spent on the control of exotic weeds in the U.S. each year. That number might double when you take golf courses into account.
But let’s get back to my hillside. I’ve been told at some garden centers that the product “Roundup” has proven effective on the Knotweed. Evidently it’s a glyphosate-based herbicide, and has been widely used for years, but I’d rather not put any more into the environment. Besides, knowing the dogs, they’d probably love to roll in the stuff.
Consulting the University of New Hampshire Cooperative Extension website, I learned, “Once established it can be difficult to remove.” Really? They recommend covering the plants with a heavy carpet, sealing the edges to the ground and leaving it in place for two months. Or you’re to remove the entire root ball but again, those can go nine feet down. If you leave as much as five grams it can come right back. Don’t leave the root ball lying about either. It has to be put in a plastic bag and left to rot. Even if I had decided to use Roundup, the website cautions to be sure you, “…make sure you pour the herbicide down each cane.”
By this time, the idea of living with the Knotweed was beginning to grow on me. In the spring the young stems can be eaten. You have to peel the fibrous outer skin, par boil it, and then cook the result to find a taste that’s described as sour rhubarb. Otherwise, as long as the lawn mower doesn’t let the stalks get too out of hand, I believe I can come to a truce with this overly enthusiastic enemy.
Allen Reese lives in New Ipswich.