More on containment
Every 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 with100% 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 be2 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.
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.
The only in-ground barrier we 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 ˝-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.
Plastic root barrier is being sold as a barrier for bamboo but we do not recommend it (with the possible exception of small ground cover bamboos). We feel it is only a temporary nuisance to bamboo. The plastic root barriers that are being manufactured today are made for trees and shrubs. We have been told that 30 and 60 mil plastic barrier materials have failed in 5 years or less when used for bamboo. Use your own judgment if you feel you must use the plastic barrier.
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 ˝ 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.
We are testing an in-ground pressure treated wood (.40 retention) barrier. It is only 24 inches deep but has a lip on the inside of the bottom with the sides sloped approximately 20 degrees to the outside. We cannot recommend this until we have had the grove contained for a minimum of 5 years.
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!