2018 Update: You STILL Can't Run Away from Running Bamboo
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This week's broadcast of Mike's Public Radio show You Bet Your Garden was taped live on the floor of the March 2018 Philadelphia Flower Show, where Mike hosts a spirited Q & A every year. Of course, there's no prepared "Question of the Week" in such a format, so we decided to instead transcribe one of the most important Q & As of that day's session—about running bamboo. Enjoy—and be warned!
Q. I planted running bamboo in my landscape that 'they' said wouldn't run; but it's run all over my garden. I want to know how I can smother or contain it…
A. OK—two types of bamboo: Good bamboo and Bad bamboo. The good ones are known as 'clumping bamboos', and many of them are dramatically beautiful. When I led a botanical tour of Cuba back in 2014 we saw some amazing varieties, one of which had culms the size of telephone poles, was the color of a nineteen-fifties candy apple green variegated muscle car and sounded like sheet metal when you rapped on one of the culms. One of the most remarkable plants I've ever seen.
Anyway, these clumping types do get larger as their culms get thicker, new culms emerge and the plants spread slowly outward over time, but their rhizomes (root systems) essentially stay in place; they don't travel underground. "Running bamboo" (aka 'bad bamboo') is just the opposite; it's rhizomes travel laterally underground at an amazingly fast pace. And it is a ridiculously hard plant to eradicate because of one unfortunate fact. You look at a grove of running bamboo and think "there's hundreds; maybe thousands of plants in there!" But no—that's one plant.
Think of the culms—the individual stalks of bamboo—as branches. Underneath those branches is the single root system of that plant. It is enormous. Again: When you see a grove of bamboo, you're looking at a single plant; and preventing the growth of that plant takes time and/or money.
Now; if you want to grow running bamboo—which is a stunningly beautiful plant—and want to be a good neighbor (and not threaten the stability of your own home), you should decide how big a grove you want and then surround that area with an underground fencing system called 'rhizome barrier' BEFORE you plant. (See this previous Question of the Week for details on the material and its installation.)
Again—if you want to deliberately grow bamboo, install rhizome barrier. Actually you should pay someone with lots of experience to do it because the last thing you want to do is buy the material, dig deep trenches and get it wrong.
Now, people think that I planted running bamboo on my property because there's a prominent stand of it nearby. I did not plant it. I inherited it. And it is not a problem for me because it is surrounded on all four sides by something that stops its forward motion. On one side is a stream (like vampires, bamboo cannot cross over running water), behind it is a solid and formidable outcropping of granite, in front is the county road and on the fourth side is my neighbor Willard, a determined Pennsylvania Dutchman who mows the new culms down weekly.
I've lived in my house for almost 35 years and the bamboo on Willard's side has not gained a single inch. Pennsylvania Dutch have a reputation for being tenacious, and now we know that they are even more tenacious than running bamboo. A truly remarkable achievement.
You CAN control the forward motion of running bamboo by repeated mowing. You can't easily make it go backwards by mowing, but if you don't miss a week it will grow no further in the mowed direction.
Back to control in a moment. Right now, we should mention that it is illegal to plant running bamboo in a growing number of municipalities in states like Pennsylvania and New Jersey. And the Supreme Court of the Commonwealth of Virginia has ruled that the person who planted the bamboo or on whose property it originates is responsible financially for any damage the bamboo does on adjacent properties. And the 'owner' is responsible for its removal from those other properties. Which is important, because this plant can take your home right off its foundation.
And if it gets into your garden, you won't be able to grow anything else there.
Control: "Rope a Dope". Repeated mowing will eventually kill the root system. First, you have to cut the existing culms back to the ground. Bamboo has a decided tendency to split and is difficult to cut cleanly, so try different types of saws and pruners and don't be afraid to import the correct types of tools from Japan. And don't forget that the harvested culms are incredibly useful material; they make excellent trellises, bean poles, arbors and such.
Then you want to rent, buy or hire a 'brush hog'—a machine that's essentially a lawn mower on steroids—to cut the stumps back to the ground. And I mean TO the ground; we want to see dirt flying here. Once it is cut down to the ground—and this has been confirmed in numerous studies—repeated cutting for around three years will exhaust the root system and the true plant itself will die.
If you allow a plant to grow but consistently stop it before it can form true leaves, you prevent that plant from photosynthesizing and the root system will die.