Bamboo
Bamboos are much misunderstood and misused in this country. Properly sited they can bring a serene, contemplative, or dramatic touch to a garden in a manner different from almost any other group of plants. Here I will hopefully present a few notes regarding their choice and use that will help encourage their planting to their best effect and without regret.
Overview
Bamboos are grasses. Grasses seem to have evolved rather late in flowering plant development, at some point during the Cretaceous (before 65 million years ago). Bamboos themselves probably evolved sometime in the Oligocene or Miocene (40-30 million years ago) according to Ted Jordan Meredith in his outstanding and highly recommended new book, Bamboo for Gardens. Bamboos are an important, treasured resource for much of the world, used for building, food, and gardening. They are native to all continents except Europe and Antarctica, though only one species (Arundinaria gigantea, Cane) is native to North America. They are usually large to giant woody plants that need more than one year to mature and flower. They have a relatively wide variety of form and growth habit, ranging from grass-like dwarfs a few inches high to timber types to scandent vines. Their is one weird, atypical, tropical, “Honey I Shrunk the Kids” species I have seen a picture of that grows as a patch of single, giant, pleated blades to 9' tall, emerging from hidden horizontal subterranean culms.
Bamboos can be eaten, used for timber, for flooring, for paper, for clothing, and for innumerable small items such as fishing rods and cooking utensils. Some look like a shaggy head of hair, others like cheerleader's pompons on a sish kabob. Some giant clumping timber types form dense, robust groves fit for siting a Swiss Family Robinson tree house in.
Good locations for seeing bamboos well used in Northern California are at Hakone Gardens in Saratoga and Strybing Arboretum in Golden Gate Park, San Francisco. In Southern California Quail Botanic Gardens in Encinatas is simply outstanding, and The Huntington Botanic Gardens in San Marino has excellent examples also.
Names and Classification
Since most bamboos flower extremely infrequently (and usually die afterwards) they have been difficult to always place well botanically. We use the American Bamboo Society names and classification. Expect changes! We list synonyms when possible to help you keep track.
Types
Besides dwarfs, medium size, and giant or timber types, bamboos can be woody or rather rarely (and mostly tropical) herbaceous. But bamboos are primarily split into two major groups: runners (leptomorphs) and clumpers (pachymorphs). The roots of runners have quite a few nodes between active nodes and the roots of clumpers have few or short internodes. The first step in using bamboos is to decide which form is appropriate. The two groups have different advantages and liabilities, which is news to many who simply consider runners to be weeds and clumpers to have all the best virtues.
Runners
First of all, as was pointed out to me by someone who made his living selling the giant running Moso bamboo (Phyllostachys heterocycla pubescens), runners (at least the large forms) are generally more open, serene, and graceful than most clumpers. They tend to have more horizontal branches and a finer, more open leaf texture compared to culm thickness. They provide soft tiered billows of dainty greeness. They bend in the wind. Most of the ‘bamboo look’ bamboos are planted for, the look found in Japanese and Chinese landscape paintings or pictures of their gardens, comes from running types. You can often walk through a grove of a large running bamboo because there is space between the culms. You can create wandering paths, and little rooms. You can string up hammocks. You can put out a little table and chairs and have lunch on a hot day. You can't do any of those things with a clumping bamboo. To be sure there are also runners that are quite dense, such as common Golden Bamboo, with its closely set internodes and low, brush branches, but in general the large types are less dense and more airy.
The smaller runners though are almost all extremely dense and thus invaluable for filling small places or containers very quickly. They need to be contained somehow or they will keep on going, and fast. They are also distinguished by a very large number of variegated foliage forms. They show a large variety of leaf shapes and sizes and can provide soft billows of ferny foliage or large, dramatic, glossy leaves. They make superb container plants and often very good focal point subjects. Most small runners are amazingly vigorous and pernicious and we strongly recommend authoritative measures of control, primarily containers or barriers.
Clumpers
Clumping bamboos increase their spread slowly .They tend to be stiffer, chunkier, much, much denser, and more robust in appearance, but not always. They tend to be larger textured and to have more upright, narrowly angled branches. They are almost always so thick as to be completely impenetrable. This is not always undesirable; sometimes this larger scale is desirable, more tropical, or dramatic. There are culm colors and configurations not found in runners. There are also graceful clumping types, often very fine textured and with a look and charm all their own, such as some of the Himalayacalamus or Drepanostachyum cultivars, but they never form open, airy groves for the landscape. Plant clumping types in multiples and they can look somewhat like a bad hair transplant if you are not careful. The clumps need to be individually considered and placed, as if you were siting picturesque rocks. The best asset of the clumping types is that they stay where you plant them. But when using clumpers you must remember you are many times not getting the classic bamboo look you are looking for. That only comes from runners, and planting runners means dealing with their liabilities. Clumping bamboos have a different ‘bamboo look.’
Liabilities of Runners
The liabilities of the running types is that they run. They can run fast. They can run deep. They can run quickly. They need to be contained in many but not all situations. Containment should be by very heavy plastic liners that come up a little above the surface. This can be hidden by leaves or even soil but most runners will quickly find this weakness and escape over the top without constant vigilance. Metal can rust, concrete can be cracked under root pressure, or cracks formed from settling or stress can be quickly exploited by enterprising root tips. The containment should be from 1-3 feet deep depending on the soil, variety, and how long before you want to deal with the roots which escape.
Interestingly one of the best virtues of the runners is that the can be contained. Ironically the naturally self-contained clumpers really can't be. Clumping types are going to increase their girth in spite of everything you throw at them. They develop enormous pressure as they spread to the outside, much like water swelling as it freezes. They need to be planted where their spread, even if slow, will never be a problem. Once it does become a problem go find a pick, a crowbar, a Sawzall and a bottle of Advil and let the fun begin!
Some such as the previously mentioned Phyllostachys need minimal containment. Some such as Semiarundinaria okuboi or Pseudosasa japonica require more robust solutions. Most fall in between. One of the best ways to container runners and make use of their virtues is to simply use them as container plants. They cheerily submit to total confinement and live happily for years. Plant a clump in a container and unless it is a fine textured, slow growing type such as Bambusa multiplex ‘Fernleaf’ it may break the container when it finally runs out of room. Of course large clumpers are used as container plants by those willing to lift and divide or replant, and some forms, such as Bambusa ventricosa, make outstanding container plants.
Next, some runners lack the vigor to be much of a problem. You rarely hear anyone complain about too much Black Bamboo (Phyllostachys nigra) because it tends to be a slow grower and there is always a taker for a division. In other cases the mat is shallow and easily removed, which is the case for most Phyllostachys. There are other situations where running is not a problem, such as those with large properties where the lack of irrigation or strong gopher pressure naturally limits the spread of the clump. Others, such as P. heterocycla and P. vivax, produce a few massive spears that are very sensitive to disturbance when emerging. Simply kicking the tip off limits the spread of the grove.
Another little used technique is simply to site the bamboo so that it receives less than full sun or regular watering. I have had many problems keeping Chimonobambusa quadrangularis contained in production here at the nursery, suffering problems of roots heading out the drainage holes and down into the ground, under groundcloth, into neighboring greenhouses or properties. I have also seen it planted outside in a garden in loose, fertile sun but just a half a day of sun, with even more restricted light in winter, where it barely has the vigor or maybe just the inclination to bother to increase at all. It remains completely where it was first sited. So merely by cutting light input and not fertilizing the owner transformed a tiger into a kitten. In that situation the plant is near a hose bib and receives quite a bit of water. Light and possibly nutrient restriction are enough to completely domesticate it.
Soil texture will also affect behavior. In that same garden, in full sunlight, under regular watering, with supplemental fertilizing, planted in very loose, sandy soil, a mature grove of the usually well behaved Phyllostachys vivax had sent a rhizome the thickness of my thigh sideways at least twenty feet from the nearest culm. It was punching through a gap in a railroad tie retaining wall a full three feet below the upper soil grade. Impressive but scary. Immediately next to it was a small stand of Phyllostachys viridis ‘Robert Young’ that was spreading so slowly it behaved as clump.
For causing death I had good results with Roundup plus a wetting agent many years ago on a large, mature clump of Golden Bamboo so I would expect it to work fine on others as well. It didn't kill it immediately but it stopped growing, then looked pretty sad when it tried to grow the next year, and the second year's application did it in. A tall, unbranched form might need to be beheaded in order to bring sprayable foliage into reach. The key is to apply between mid summer and early winter when resources are being sent back into the root system. Spraying from late winter through early summer will only kill the tops. Check for current instructions and labelling.
Liabilities of Clumpers
Besides their sometimes stifled appearance the primary problem is that they deeply resent any attempt to further limit their already slow growth. As mentioned above, they tend to burst any containment. They are also prone to bamboo mealybug (see below), an obnoxious little nuisance that colonizes the joints of major and minor branches and only seems to live on clumping types. Clumps can be tough to thin out, with stems packed so thickly it is hard to fit a saw into.
Pests
Primarily these are bamboo mites, two spotted mites, and aphids. Close up bamboo mites look almost like regular two-spotted mites. Their damage is different though, being large, blotchy pale yellow or whitish discolored areas on the foliage. Two spotted mites can also cause damage, especially in drier situations. Damage is the typical minute whitish stippling found on other plants. Both are actually well controlled and even eliminated by predatory mites, Phytoseulis persimillis, at least under our local conditions. We use the predators regularly on our production plants and keep the two-spot free and while we don't have bamboo mites I have seen the predators work well on a large outdoor planting in Santa Cruz.
Aphids can be a problem and is usually indicated by black sooty mold growing on their residue. Ants farm them also and often need to be controlled to completely eliminate the aphids. Once ants are controlled aphids will usually disappear in outdoor plantings from naturally occuring parasites and predators. We use soft chemical sprays (soaps, oils, Neem extracts, etc.) and/or parasitic and predatory controls when necessary, which is not very often.
Bamboo mealybugs, as mentioned above, are an occasional problem on clumping types. Ants happily spread them around. Control is best with multiple applications of organophosphates but you will have to deal with the ants at some point as well or you will never fully eradicate them.
Some Runners
Phyllostachys, Arundinaria, Pseudosasa, Chimonobambusa, Pleioblastus, Shibataea
Some Clumpers
Bambusa, Otatea, Chusquea, Drepanostachyum
rev 11/2007