This article appears in the booklet, Landscaping Indoors, Bringing the Garden Inside, #165. Published by the Brooklyn Botanical Garden, ISBN 1-889538-18-3, and sells for $9.95.
Imagine yourself enclosed deep within a bamboo grove, a “living room” of green, with walls enveloping but breathing, the ceiling a cathedral of vertical stems stretching to the heavens above, the shadows delicate and swaying. You feel quiet and contemplative and calm, protected. Are you in Kyoto, Bangkok, or Bali? No, you are here, at home, surrounded by nurtured bamboos in containers. It is not difficult to create your own bamboo grove indoors - try it! It could be said that bamboo is the most mysterious plant in the world. Once thought to be among the most primitive of grasses, it has now been found (by means of DNA testing) to be one of the most highly evolved.
Flowering of some species occurs only once in a hundred years, while other species bloom annually or only sporadically. And, in the landscape, bamboo has the reputation of the invasive beast, an uncontrollable nuisance, and yet the cold-hardiest of the bamboos do not run at all, but form dense clumps from well-behaved root systems Bamboo evokes the essential color of green, and yet there exists myriad cultivated varieties with yellow, gold, burgundy, blue and even black stems. Some have leaves displaying intense variegation of gold and white.
The term bamboo refers to plants of the large subfamily of Bambusoideae within the family Gramineae (Poaceae). It embraces a considerable diversity of grasses, with representatives that grow only a few inches in height with vigorous rhizome root systems to giants of the tropics that can attain over 100 feet with woody, trunk-like stems rising from great clumps. There are herbaceous bamboos living on the forest floor in the tropics, too, and cold temperate clumpers above timber line in the Himalayas.
Bamboos are forest grasses, and their life cycle, structure, ecology, and management must be understood within this context. Many of these bamboos make wonderful indoor companions. With over 1,200 known forms, there is a bamboo for almost any situation, from low light levels to bright sun. Because there are so many types of bamboo to consider, and because their native homelands are often extreme in climates, it is difficult to make rules that apply to all types of bamboo. This is especially true when growing bamboo indoors.
Bamboos are really no different from the more “usual” houseplants, and require the same amenities: well-drained and nutrient-rich soil, sufficient light, adequate humidity and fertilizer during the growing season. Remember, true bamboos cannot grow in standing water. True bamboos are grasses, and grasses love to eat. As flowering is rare and sometimes detrimental (consuming the plant’s vigor) in bamboos, it is best to feed with a high-nitrogen, low potash fertilizer, i.e. water-soluble 30-10-10, although really most any balanced N-P-K fertilizer solution will do. Slow-release fertilizers like Osmocote 28-14-14 or Sierra 17-6-10 Plus Minors can be mixed into the soil for a complete feeding, as per manufacturers directions.
When growing bamboo in containers, it is important to use a pot with adequate room for these fast-growing plants. Use a container large enough to have a space at least two inches between the edge of the root ball and the side of the container. Squatty tub-like containers are generally better than tall, deep ones, especially for the “running” bamboos with rhizome roots that typically grow more horizontally than down deep. Bamboos with clumping root systems do not need such frequent repotting and rhizome pruning as the running kinds. Any type of bamboo will spread within the container and eventually become pot-bound. Large plants require voluminous containers. Once the bamboo completely fills the pot with root and rhizome, it will need to either be moved to a larger container - or, as with bonsai culture, growth can be restricted by removing the plant from the container, removing some of the roots (approximately one third of the total) and upon placing the plant back into the original pot, replanting with fresh soil.
The generalization can be made that the larger the leaf, the less light it requires, but one also needs to take into account whether the bamboo is natively tropical or temperate. Temperate bamboos refer to the fact that the species is indigenous to a climate that provides a cold dormancy. When temperate bamboos are grown indoors, their environment is altered and the cold dormancy is not achieved. This is not damaging to the plant, but often results in leaf drop. Aesthetically, and in terms of maintenance (house-keeping!), this must be understood, as the bamboo can appear almost naked, and water requirements are affected. It is the short days (lower light levels) that have triggered the dormancy (not the outdoor cold), and the plant is “resting.” Since photosynthesis has slowed, water is not consumed. This is important to note, as bamboos do not enjoy saturated soils and one must be careful not to over water. Saturated soils leave no room for oxygen, and without oxygen, the roots will rot and kill the plant.
In contrast, tropical bamboos are found in warm climates in which temperatures remain more or less consistent throughout the year, as does the length of day. Tropical bamboos grown indoors adjust to the indoor environment with less trauma and acclimate more easily. They, too, will react to gradual change in day lengths but, with consistent temperatures and moisture content, will continue their growth cycles without noticeable side effects. Supplemental lighting is easy to provide and can truly create evening ambiance as well. Don’t limit yourself to those industrial fluorescent tubes; wide-spectrum bulbs can be incorporated into myriad fixture types. Another tip to keeping your bamboo happy is that the higher the air temperature, the brighter the light must be for successful indoor culture. This seems to apply mostly to the temperate bamboos in the winter, who would like a rest. Since the light intensity is low in the winter, they would prefer cooler temperatures as well. This is particularly true for many species of Phyllostachys. Coolness seems to offset low humidity. To increase humidity, place containers on a bed of pebbles with a little water under them, or use humidifiers to create an atmosphere of moisture. Grouping plants together accomplishes this easily. Misting the plants occasionally with a spray bottle is another easy task, and helps alleviate dust build-up. Not only do plants need water, food, and light, they need care.
The key to keeping bamboo beautiful is an occasional manicure. If you are growing a taller bamboo for its strong vertical culms (the proper name for the stems of woody grasses; it becomes a “cane” once it is cut), then regular thinning and pruning will keep the bamboo plant looking its best. Remove unwanted, “wimpy” or withered culms by cutting off at soil level. Control the height of any culm by cutting just above the node (the place on the stem just above a branch). If the bamboo is stretching beyond what your home ceiling allows, it will not suffer at all from being “topped.” Simply cut the culm just above the topmost branch. These same bamboos that are being grown for their height and culm character (black, for example, or colorfully-striped), really benefit aesthetically, and mimic greater age, if the lower portion of the culm is bare of branches. Cut the branches from the culms along the bottom-third of the plant (do not leave stubs), and shorten the branches to the second node of each branch to further emphasize the culm. You mustn’t be afraid to prune the bamboo. It is tolerant and forgiving, and will appreciate the attention.
A shallow bonsai container can become an indoor turf of the low-growing bamboo Pleioblastus distichus, a species from Japan that only grows to a height of 6 inches. For dramatic color, the variegated form of Hibanobambusa tranquillans ‘Shiroshima’ is fantastic, growing to a height of 8-10 feet with an architectural silhouette of branches stretching out half again as wide. Its leaf blades are large (approximately 6 inches long) and each leaf shows a unique pattern of many creamy, white stripes. For that "grove cathedral effect" mentioned earlier, try large containers of Bambusa ventricosa or Phyllostachys nigra.
Most of these above-mentioned bamboos can be very successfully used in combination planting, i.e. using a tall bamboo under-planted with a lower-growing form. (see photo) All are compatible with many other types of plants, i.e. under-planted with anthuriums, philodendrons, helliconias, passifloras, etc. One is only limited to the size of the container and one’s imagination !
Bamboo is one of the most mysterious plants in the world - but not because it is difficult to grow. Its mysteries lie in its ability to thrive and delight and evoke emotion. A symbol of longevity, wisdom, strength and flexibility throughout cultures around the world, bamboo has a human connection few other plants can rival. Bring these fascinating bamboos into your indoor landscape and experience their beauty firsthand.