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MARTHA SEZ: ‘The knotweed outlived the gardener’

July 26, 2019
By MARTHA ALLEN , Lake Placid News

When it comes to paying bills, I am the embodiment of the classic Dagwood and Blondie struggle.

As a child, I followed Chic Young's cartoon strip "Blondie" in the Sunday funny paper. Dagwood sat at his desk, overwhelmed by towering stacks of bills, while Blondie blithely shopped for shoes, or came home with her arms full of boxes and shopping bags.

I am both Dagwood and Blondie, fretting over how I will pay my bills, while at the same time tempted by shopping opportunities, temptation augmented by the Internet. Blondie had to go to the shoe store, but we can run up bills without leaving the house.

I spend too much money on seeds, bulbs and potted plants, and much of what I buy goes to waste. My garden never turns out according to plan, but nonetheless I am endlessly fascinated by the possibilities. I can understand how the dread knotweed invasion got started.

Probably it was enthusiastic gardeners, excited by the introduction of these vigorous, hollow-stemmed flowering plants, also called Japanese bamboo, who established them around the country. Who could they have known just how vigorous knotweed plants would prove to be? Who could have imagined how they would take over, or that they would prove to be practically impossible to eradicate?

I have watched a stand of Japanese knotweed as it grew from year to year. Years ago, it was planted by a gardener who bought a plant at a nursery. He had no idea of the monster he was creating. When he came to understand knotweed's invasive nature, he tried, unsuccessfully, to kill it off. The knotweed outlived the gardener, and is flourishing to this day.

Knotweed, a member of the buckwheat family, was brought to the United States, Europe and England from China, Korea and Japan in the late 1800s, planted as an ornamental and also to control erosion. Knotweed is happy just about anywhere, growing as tall as 15 feet. It thrives in full sun, but does just fine in deep shade. It loves to grow along the banks of rivers and streams, but drought and summer heat? No problem. It doesn't mind a little salt in its soil. Knotweed doesn't invade deep forest, fortunately, but where the ground is disturbed, and around old homesteads, it will take hold and proliferate.

After the first hard freeze knotweed plants will look dead. During the winter all signs of them will disappear. You might think, oh, knotweed is an annual after all! If so, you will be wrong. Winter cold does not kill off the root system, which merely lies dormant underground, waiting for spring. When the ground thaws, plants spring up all along the length of the rhizome, forming dense thickets.

Japanese Knotweed can grow up to 8 inches a day. The roots form a dense network growing 9 feet deep into the ground and spreading 20 feet or more in all directions, which can cause structural problems in buildings. Knotweed on a property can adversely affect real estate sales.

There are several types of knotweed, including Polygonum x bohemicum, Polygonum cuspidatum and Polygonum sachalinense. They can interbreed. In England, all Japanese knotweed populations are clones of a single female genotype and do not produce pollen. Only female plants were originally introduced, and so the plants don't produce pollen or viable seed. However, they are able to accept pollen from other types of knotweed, producing fertile hybrids.

In some areas of the United States, knotweed spreads by its root and rhizome system, while in other areas knotweed stands produce copious amounts of fertile seed. The smallest piece of rhizome will take root and grow.

The knotweed stand I observed grew larger every year, and the individual bushes were also taller and fuller. The aggressive proliferation of these plants gave me the creeps. On the other hand, I can see why gardeners were tempted to buy and plant knotweed in the first place.

The young shoots can be eaten by humans and are loved by goats. The heart-shaped leaves are lush and green, and in the late summer and fall the branches are covered with clusters of sweet-smelling white flowers. These flowers are visited by many insects, which at first I took to be bees, but which on closer inspection appeared to be mostly various kinds of flies. I would prefer, of course, that they were bees, but still, the overall effect was very pleasant.

Have a good week.



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