Containing bamboo is a matter of diligence. The excellent article below first appeared in the Southeast Chapter American Bamboo Society Newsletter (Volume 8 Number 1). Reprinted with permission of the author.
There are two main methods used to contain running bamboos. You can either install a physical barrier or use cultural methods to keep it in bounds.
A physical barrier has the advantage of being permanent (if well designed) and needing minimal effort afterwards to keep the bamboo within. Its drawbacks are the expense of the barrier material, and the labor needed to dig a trench and install the barrier. Barriers may be made of HDPE, fiberglass sheets, sheet metal, and various other composite materials. It needs to go at least 2' deep and be slanted with the top away from the bamboo side of the barrier. This forces any rhizomes up to the surface where you can see and cut them as they try to get over the top of the barrier. Bamboos tend to be deeper rooted in lighter soils, so if you're on light sandy soil, go down 3' ; if you're on heavy rocky clay, you might get away with 1' to 1.5'. The top of the barrier needs to be 2"- 3" above the soil line so it doesn't get buried by subsequent year's accumulations of leaves and soil and any mulch you might add. Joints in the barrier material need to be securely fastened to prevent the bamboo rhizomes from worming their way through any cracks that might be at the joints. Once installed, all you'll need to do is walk along the barrier once or twice toward the end of summer to spot and cut any rhizomes that are trying to jump over the top of the barrier and, also to make sure all of the barrier top is still exposed above the soil line. The saturated soil along a stream or swamp can serve as a natural barrier that will contain most bamboos, except for possibly Phyllostachys purpurata, which is said to be able to grow into shallow water.
There are various cultural methods of controlling bamboo. Cultural methods are cheap but require some of your labor at a specific time of the year to control the bamboo. If you skip a year when using these methods, then you have a lot of work ahead of you to get caught back up with the bamboo. One cultural method is simply each spring to cut any shoots coming up outside the area you designate as "bamboo grove". You can either cook up and eat the cut shoots or throw them into the bamboo grove to compost. If your bamboo is surrounded by lawn, then just mow frequently over the area where the bamboo is coming up during the spring shooting season. This is how the Moso grove at the Old Silverbrook Cemetery has been controlled for the past 70-odd years. It is contained on two sides by a stream and swamp, on the third side by mowing a strip about 80’ wide and on the fourth side there is a one lane asphalt road which it hasn’t yet been able to burrow under.
An alternative cultural method is cut in late summer a 1' deep line along the edge of your bamboo grove with a shovel (or cut 2’ deep with a ditching machine, if you have one). The best shovel for this is one of those long handled, flat, straight edged transplanting shovels. What you are doing is cutting any bamboo rhizomes that have spread beyond the grove during the summer and these young rhizomes aren't capable yet of surviving on their own. The first year you do this on the edge of an established grove is going to be tough digging since you are having to cut through the old hardened rhizome mat, but once the line is established, subsequent year's cuts are much easier, since the current year's rhizomes are soft and easily cut. Once established, its just a matter of going through and "chop-chop-chop-chop" down along the line with your shovel in late September of each year. When using this method, every now and then a deep running rhizome will escape your cuts and will send up shoots outside the grove. When this happens, cut out the shoots and dig back along the rhizome and remove it. A variation of this method is to dig and maintain a narrow trench 2' deep around your grove and then simply to cut any rhizomes you see trying the "bridge the gap" across the trench. Running bamboos spend the first part of the summer (through June) growing new culms, and remainder of the summer extending their rhizomes. So any rhizomes you cut in October are only a few months old.
If your bamboo has already escaped and you are trying to get it back in bounds again, the first thing to do is to cut off the part of the bamboo that's gotten where you don't want it from the part you wish to keep. You can use either a ditch digging machine or the shovel described previously to cut a line between these two parts. If it's an old established grove, cutting this line can be a tedious job.
Once you've severed off the part of the bamboo grove you don't want, then there are several ways to get rid of the unwanted portion depending on how large an area it covers, what other plants it's growing among, and how well established and dense the unwanted bamboo is. Various methods to get rid of it include. 1) Persistently cutting back the top growth until it finally weakens and dies (this will take a couple of months). 2) Cut it back and use a contact herbicide on the new growth coming up (bamboo is fairly resistant to a lot of herbicides so it may take several applications to kill it out completely). 3) Cut it back and lay black plastic over the area to shade out any new growth coming up (if you do this doing the summer in a sunny spot you're also heat sterilizing to kill any nematodes and weed seedlings that sprout in the upper layer of topsoil). 4) If there only a small amount of escaped bamboo, then just follow and dig up the escaped rhizomes (kind of like following and digging up an underground cable), although if there are a lot of roots in the area this method can become difficult. 5) Cut it back and pen a goat or hog over the area. After a month or two you'll have no bamboo and a fat animal. 6) Cut it back and then rototill or deep plow the area. Then go through with a rake and pick out all of the pieces of rhizome in the turned over soil. Repeat the plowing and picking steps several times to be sure you have gotten all of the pieces out of the ground.
More on containmentEvery bamboo grove stops somewhere because somebody or something contained it. Just remember that bamboo has been on the earth for over 20 million years and to the best of my knowledge it has not taken over the world...
Temperate bamboos spread by underground rhizomes, woody stems that resemble the above-ground culms (poles or canes). The rhizome has nodes and internodes just like the culm. While the culm produces branches, the rhizome will produce feeder roots and/or a rhizome side branch and/or a new above-ground culm.
There are several methods to contain bamboo and keep it from spreading where you don’t want it. We use several of the methods we will try to describe below and hope it will help you select a method that is appropriate for you.
First -- you should consider your age, health, amount of time you have to maintain your grove, your budget and anything else your personal situation may require.
The methods we will describe are by no means an exhaustive list but those methods we know about or use ourselves. No one method will be best for every one so consider your location and personal situation before selecting the containment method for your bamboo.
Our personal experience with clumping bamboo planted in the ground is limited to some Bambusas. They all are die-back perennials for us with 100% top kill every year. Our climate is too cold for the tropical and sub-tropical varieties and too hot and humid for the temperate clumpers.
Clumping bamboos do not spread like temperate bamboos, but expand, usually in a circular manner. If your climate will support a clumping bamboo, be sure to allow for the expansion. Do not plant near a foundation as the pressure exerted by a clumping bamboo can be considerable and could possibly damage the foundation. If planting on a property line, be sure to allow plenty of room between your bamboo and the line as it is extremely difficult to keep a clumping bamboo cut back to the property line if it should cross. In 5 years our Bambusa multiplex Tiny Fern (with 100% top kill each year) has gone from a 4” start to 30” in diameter.
We have no recommendations on containing clumping bamboos.
Natural barriers provide the easiest methods of containing bamboo. Water is the usual natural barrier used for containing bamboo. None of the temperate bamboos we sell except for tumidissinoda will cross standing water -- lake, pond, year round creek, river, etc. An underground rock ledge will divert bamboo. A very hard-packed road will retard a bamboo and keep it in control. The time the road will control bamboo depends on the width, the sub soil, weather and all the usual variables. Although we have no actual knowledge to verify this, we feel that it could take 20 years or more for a bamboo to cross a well-traveled, hard-packed road.
Planting a bamboo rated for full sun in full shade (100% canopy) will reduce the spread of bamboo; it will slow the spread down to a crawl compared to the spread planted in full sun.
Pots, containers and planters…
When referring to pots, containers and planters we are talking about above-ground containers for bamboo and the terms can be interchangeable. Pots usually refer to containers 2 feet in diameter or less, containers would be 2 to 3 feet in diameter and planters describes any container larger than 3 feet in diameter (2 feet x 8 feet, etc.). The larger the variety you plan to keep in a container, the deeper the container needs to be. We recommend 12 to 16 inches minimum.
The principles are the same for all with the main variable being the time required for dividing.
When selecting or building a container be sure to get one with the sides sloping out (the top larger than the base). This will encourage the rhizomes to deflect up and out of the pot instead of traveling downward. Then when you see a rhizome emerge, you can trim it off. It is also much easier to remove a bamboo from a container of this shape when the time comes to divide the plant.
Plastic, pressure treated lumber (treated to .40 retention), concrete, concrete blocks, bricks and fiberglass are some of the materials you could use. Do not use terra cotta or porcelain as bamboo will burst these in short order.
Watering requirements are different based on local conditions; however, you will soon determine the correct amount of water required based on your bamboo’s leaves. When the leaves curl, the bamboo needs water. Do not over water.
The most important thing is dividing your bamboo on a regular basis. The time between dividing will depend on many factors, but you will soon learn when to divide as it will become more and more difficult to keep your bamboo watered. A general guide: in pots, usually every 2 to 3 years, in containers every 2 to 4 years and in planters every 3 to 6 years. The best way to divide your bamboo in pots is to remove the pot and, using a pruning bow saw, cut the root ball in two to three sections repotting each as a separate plant. In containers and planters we recommend our Bamboo Spade or the King of Spades. Replant the divisions in new containers or planters.
Because of safety concerns for those touring our groves we do not use trenching; however, we are told that trenching is a very effective method of control. To control by trenching, dig a trench 8 to 12 inches wide by 12 inches deep. Then watch the trench for any rhizomes that try to cross and cut them off.
Define the area where you want your bamboo to stop and mow every time you mow your grass. Allow a distance equal to the rated height of the bamboo to be sure it doesn’t cross the property line. That is, if the variety you have is rated for 25 feet, allow 25 feet of mowing area in any direction where you don’t want bamboo. Mowing must be done regularly or you will have to go in with a saw to cut down culms to get the grove back to your defined area.
Locate the defined area for your bamboo and in July and October make overlapping cuts in the soil 10 to 12 inches deep with our Bamboo Spade or the King of Spades. Make sure all the cuts overlap to be sure you have cut all rhizomes. Cut any culms that should come up out of bounds. This must be done every year or again -- get out your saw.
A tractor with a subsoiling attachment comes in handy for this as well.
Mowing and rhizome pruning…
Make overlapping cuts as described above every October; then mow all the out bound shoots. This is the main method we use to keep our bamboo contained to defined areas.
The Chinese say the best way to contain bamboo is to eat it. By this they mean that you harvest all the shoots that come up to use as a fresh vegetable. See our recipe pages for information on how to use fresh shoots.
In our opinion, the best in-ground barrier we can recommend is 4-inch thick reinforced concrete. You can hire a landscaper to do this or do it yourself. Make a 4-inch wide by 36-inch deep trench at your defined area. Form with 2x4s so you will have a 1 ½-inch curb and fill the trench 1 foot at a time inserting a 3/8 inch rebar horizontally at 1-foot and 2-foot levels. You could use rewire if you prefer. The purpose of the reinforcing is to keep the cracks that form in the concrete from separating. The curb is so you can easily see any rhizomes that try to escape and cut them off.
We have used 1,000-gallon steel oil tanks cut in half with drainage holes and buried with 3 inches exposed. We also have used a number of nylon containers we found at a junk dealer. The containers are 4x4x4 feet and ½ inch thick. We cut them in half and buried them with 2 inches above ground. The top half with no bottom has allowed bamboo to escape by going under the 2-foot height in 5 years. The half with the bottoms and drain holes has not had a bamboo escape in 7 years. We always check the junk shops looking for more of these containers but have not yet found more of them.
The newest in-ground barrier on the market is High Density Polyethylene (HDPE). This is a relatively thick, yet pliable material that comes in various sizes and thicknesses. It is easier to install than a concrete barrier and likely less expensive. We recommend a minimum depth of 30" and 60 mil thickness. We sell DeepRoot brand HDPE bamboo barrier in 30" and 36" depths in 60 and 80 mil thickness. We can get special order larger sizes and thicknesses as well.
The key to containing bamboo is diligence. As a general rule, for a single grove you can perform all your maintenance, containing and grooming in 8 hours or less per year. Don’t skip a year or you will have to use a saw to get your grove back in bounds. Consider your budget, your health and physical abilities and the time you are willing to put into containing your bamboo; select a method that meets your situation and enjoy your bamboo!