Bamboos are tropical or warm-temperate grasses with mostly evergreen leaves. Bamboos range in size from several inches high to more than 100 feet for the largest tropical species.Bamboo "canes," known as culms, grow from a branching underground root structure known as a rhizome. The branching habit of the rhizome determines the growth habit of the bamboo. Clumping bamboos have rhizomes that grow only a short distance before sending up new culms. Most clumping bamboos cannot tolerate more than a few degrees of frost. Running bamboos have rhizomes that produce long offshoots before sending up new culms. It is the more aggressive species of running bamboo that have caused bamboo to suffer so much bad press. Many running bamboos can tolerate frost down to about 0 degrees F or lower.
Bamboo follows an annual growth cycle that is somewhat different from other plants. For running bamboos, this cycle begins with the onset of warm weather in March or April. At this time, last year's leaves are shed on the older culms and replaced with new leaves. This process has led to an unusual Japanese term for the spring season: "Bamboo autumn." At about the same time, new shoots emerge from the underground rhizome. Within a matter of weeks, most of the bamboo shoots "telescope" into new culms. The growth rate of the culms during these few weeks can be very rapid, especially in the larger bamboo species.
Once the culm has grown to its full height, all vertical growth ceases. Gradually side branches appear on the new culm, followed by leaves. The culms does not become entirely woody until its third or fourth year. Individual culms rarely live for more than ten years and start to decline after about the fifth year.
Clumping bamboos follow a slightly different growth cycle. New growth usually begins in June or July with the onset of hot, rainy weather. Shooting continues most of the summer and can continue until frost. On clumping bamboos, the new culms will often not develop branches or leaves until the next summer. Most of the below-ground growth of bamboo occurs in the late summer and fall. At this time the bamboo rhizomes put out new underground branches in preparation for the next year's growth.
Bamboo grows best in moist, fertile, well-drained soil such as might be found on the bank of a river or creek. The Southeast's single native species of bamboo, Arundinaria gigantea, is commonly referred to as "river cane." Bamboo cannot grow in swampy soil that is waterlogged all year. Bamboo grows well in sandy soil and very well in red clay. In Japan, where red clay is scarce, it is common practice to top-dress the soil under certain species of bamboo with an inch or so of red clay.
An established grove of bamboo will grow well with an annual, light application of a lawn fertilizer. Fertilizer is usually applied in February or March before shooting begins. For an established grove, irrigation is generally only necessary during droughts. More vigorous growth can be attained by following the same fertilizer and irrigation program that is locally recommended for Bermuda grass.
Bamboo rarely flowers, sometimes only once every hundred years or so. The reluctance of bamboo to flower and set seed has kept exotic bamboos from becoming the same sort of ecological monster as have kudzu, Japanese honeysuckle, and privet. When bamboo does flower, it can be very detrimental to the plant. In some species, flowering quickly leads to the death of the plant. However, the flowering process can often be halted by heavy application of lawn fertilizer, followed by ample irrigation. This should be done at the first sign of flowering. Bamboo flowers are small, grass-like, and appear in the mid-spring.
Because bamboo flowers so rarely, it is usually propagated by division. The best time to transplant most bamboos is in the early spring before the new shoots appear. The larger the size of the transplant, the higher the probability of success. It is possible to transplant only the rhizomes with some success, but transplants are more likely to succeed if some of the culms are moved with transplanted rhizome. The top half of the culms should be cut off to reduce water loss. The roots of the plant should be kept moist until it can be planted in the ground.
Once the plant has been moved it should be lightly fertilized with lawn fertilizer and watered heavily for a week or two. The transplanted clump should be watered regularly during the first summer if natural rainfall is lacking.
PLANTING and SPACING
The main requirement in planting is to make sure that there are no air pockets around the root ball (this means that when back-filling, the soil should be well tamped and gently compacted around the plant). We like to plant the bamboo an inch or two below the existing grade, or to make a small moat or dish around the plant to facilitate the initial feeding and watering.
If you have clayey or highly compacted soil, your goal will be to loosen and aerate the soil. On a small scale, and for an initial fix, this means a shovel &/or a spading fork. On a large scale this means either digging holes with a backhoe (and amending the mix within) or ripping with a tractor. For long term solutions to clayey and highly compacted soils, good organic compost and mulch (applied once or twice a year) are very good allies.
Dig a hole the size of the pot then remove the plant from the pot. If the plant is extremely full in its pot, and if you feel bumps around the outside of the pot, then you will have to cut the pot to remove the plant. BE VERY CAREFUL NOT TO DAMAGE THE NEW BUDS (the bumps you feel when you run your hands over the outside of the pot) when you do this. Set the plant in the hole so that the soil with the plant is just slightly below the grade of the existing soil. Make sure that there are no air pockets around the root ball. Pull all the weeds for a diameter of about a foot all the way around the plant. Many fertilizers designed for grasses and palms will work. Avoid any products with very high nitrogen on young plants as you can burn the roots. Compost is good. If mineral supplements are not present in your fertilizer we recommend adding some. Ask your local Ag Extension agent what is best for your particular conditions.
Water well, and mulch heavily. Most bamboos donít like to have their feet wet all the time. They like to dry out a bit between watering. If you live where the grass does not stay green you will probably need to water the plants 1-4 times a week depending on the species and the time of year. During the months between Spring and early Fall, the plants will probably use more water than during the winter.
Bamboos can be spaced according to your goals. Plant closer together for a wall or windbreak, farther apart for a screen; or create an open grid if you are managing your plants in order to harvest lumber or edible shoots. Your spacing will vary by species.
The closest spacing we ever recommend is to place the holes 4 feet "on center" (that means that the centers of the holes are 4 feet apart from each other); for a species like Malay Dwarf (B. glaucophylla) this would result in a dense wall of bamboo. For species like Dendrocalamus membranaceous, you could get a wall of bamboo by placing them 12-15 ft. apart "on center" (assuming sufficient water). If you are planting with the intent of harvesting for lumber or shoots, grids of 15-25 ft. are in common use (depending on the species in use) to allow sufficient room to work.
WATERING and IRRIGATION
Some basic considerations are rainfall, humidity, wind, and soil type & condition.
From the time you first plant your bamboo, until the end of it's first summer of growth, you will need to make sure that it has enough water, but also that it does not drown. If you have soil that drains well, then no problem, but if you have heavy, clayey soil, or highly compacted soil, you will need to address this before planting your bamboo (see above).
Your actual watering plan will depend on your climate and soil, this could mean no irrigation at all, or a well designed drip irrigation system that puts water on the plant every day - there are many variations in between these two extremes. You want to wet the whole root ball of the bamboo - to its base. Bamboos like to dry out a bit between watering. It is good to remember that bamboos get their oxygen from the air in the soil - highly compacted soils and totally water-saturated soils defeat this.
The drip irrigation system that we like goes
like this - A ĺ inch or 1 inch "mainline" that feeds:
In the "main line" use an in-line "T" for each plant. Use the Netafim fittings to get from the "T" into the Netafim that will surround the bamboo.
For 1-gallon size plants, you only need to put one ring around the bamboo. For larger plants we use a double ring. The first ring makes a circumference right at the base of the plant (close to the canes), and the second ring makes a circumference about a foot to a foot and a half outside of the first ring. Each year you can/should adjust these rings to accommodate the new size of the plant. On some of the really large diameter bamboos you may want to put a line to two that bisect the diameter of the plant.
FERTILIZING, COMPOST and MULCH
Clumping -Non-Invasive - bamboos do most of their above ground growth during the "summer" (in Hawaii this is roughly May-October). Starting in April, we recommend fertilizing with an organic - quick release - fertilizer with an application every 4-6 weeks, depending on rainfall/irrigation. During the first season of growth we recommend using a fertilizer with a Nitrogen value of no more than 10. After the plant is established, higher Nitrogen amounts can be used safely. The actual formula (N, P, K), including some particular complement of minor nutrients and minerals should be determined by your particular soil type - consult your local nursery, horticulturist, agronomist, USDA Soil Conservation Service, or agricultural extension service agent (usually through a university). Whatever formula you choose, be careful with Boron - it should only be used in very low dosages.
Healthy soil is our greatest resource for healthy plants. Compost and mulch result in healthier soil, healthier plants, and ultimately in less work. If applying fresh (green) wood-chips as mulch, make sure that there is ample Nitrogen underneath the mulch to feed both the microorganisms and the bamboos.
After this initial thinning:
You can also prune out branches to reveal the canes or to create a more airy feeling. If you are of a mind to have a highly manicured hedge you can use hedge trimmers to create whatever shapes you like (this is more easily accomplished with the smaller varieties - Bambusa multiplexes, B. glaucophylla, etc.). This shaping can become topiary for those that are so disposed - check out what they do in Thailand with Monastery Bamboo (T. siamensis).
Keeping a "LARGE" BAMBOO in a "small" space
It is possible to keep bamboos smaller than their normal size by over thinning. If you cut out sufficient plant material, including some of the newer growth (you will have to determine the actual amount by trial and error), you will diminish the plant's ability to make larger canes in the following season. We recommend waiting until the bamboo has gone through two full growing seasons before starting to do this.
- If you take an existing, well established clump & clear-cut it (i.e. cut every cane at just above ground level), that clump will put up numerous small shoots in its following summer. Succeeding generations of canes will increase in size year by year. At some point in this succession the canes will approach the size you desire. At this point in the process you can effectively keep the bamboo at that size by selective pruning - this selectivity will include some (but not all) of new growth, and some of the older canes as well. Again, trial & error will be your best teacher.
BAMBOOS IN POTS - outdoors and for interiorscape
Bamboos are used in containers, both in the interior and out of doors. Not all the species are easily adaptable to this usage but a great many of them are.
At the nursery, we use black plastic pots because they are cheap and available. They are not designed to keep plants in over a long period of time. If you are keeping a plant (not just bamboos) in a container we think you should transfer the plant into a pot that "breathes". The old-style unglazed terra cotta pots are perfect. They allow the roots to stay cool and allow moisture and oxygen to move freely. Bamboos like to be wet and then dry out. Make certain the pot has adequate drainage. Make certain that your planting mix is not too dense or it will retain too much moisture. If they are kept wet continually the new buds are likely to rot. This will prevent new growth from occurring. Try lightening your mix with black cinder (if it is available) or perlite. Do not bump up the size of the pot radically. This will generally encourage over-watering and will again result in a high probability of rotting the new growth. We generally move from a one-gallon pot to a 4 or 5 gallon pot. From there we often jump to a 10-gallon pot.
Imagine yourself in a black rubber suit out in the sun. Then think of your plants. Especially if your plants are outdoors, please take them out of those black plastic pots. Their poor little roots are baking as we speak. And when you water them, those roots stew.. not a pretty picture. If you must leave them in those pots make certain that the pots are not in direct sun. Place the pots in baskets or throw palm fronds on them. Anything. It's also easier on the plant, though not essential, to be in indirect or filtered light.
While plants in the ground tolerate a substantial amount of abuse gracefully, plants in pots, especially those in the sun, are less forgiving. Depending on the size of the plant in relation to the size of the pot, as well as your particular environment, these plants might need to be watered daily. Best time is early morning or late afternoon. If you are watering during the day and are using an outdoor hose please make certain the water is not hot.
One of the most important things to keep in mind is that when you go to the mall, or the doctor's office, or a nice restaurant, and you see those lovely perfect looking plants it is highly likely that those plants are being rotated. If you want interior plants looking primo at all times we suggest you have 2 sets of plants that you move in and out from time to time. This is what the professionals do and it is what works. However, if you have realistic expectations and remember that your plants are living creatures not all that different from you (with good hair days and bad hair days) you can work around it.
Once more we would like to stress the advisability of
removing the plants from their plastic containers and planting them in a
well drained mix. It seems better to us to have to water more often than
to risk waterlogged plants. We also like to keep a bit of air moving
under the planter and so for smaller containers we lift them from their
saucers on chopsticks. For larger containers find some larger dowel or
some other appropriate material. You will have to determine what the
correct watering regime is for your particular situation. Often,
especially in the cooler months, once or twice a week is adequate. In
the warmer months (during the shooting season) it might become necessary
to water your plants more often. They will tell you if you stay in
communication with them.
Please do not try keeping interior plants in hermetically sealed environments. Air motion is essential. If your doors and windows don't open don't even try it. It is an exercise in futility.
Here are some good choices for plants in pots: