Most people regard bamboo as a large, beautiful, invasive plant that is found in warmer climes, but it is really just a grass. Giant bamboo forests are found in Southeast Asia, but the plant is grown in many forms all over the world, even in high mountains. Bamboos are classified by their rhizome root propagations: either runners (tend to be temperate) or clumpers (tend to be tropical). Bamboo is anchored and nourished by a thick underground network of roots, called rhizomes. Running bamboo propagates in all directions, sending up shoots that grow vertically extremely fast. Clumping bamboo grows - bunched together – in dense circular groupings. In both cases, the shoots become clums. Nodes form at the end of each clum, separating one hollow segment from another as the bamboo grows vertically. Segmented branches grow from the nodes, and produce leaves and very rarely, flowers. Bamboo plants are evergreen, and dropping their leaves in the fall, and growing new ones in the spring. Bamboo can be as small as one foot tall at maturity, and other species can mature at over 100 ft in height.
Bamboo is an excellent houseplant and makes beautiful bonsai as well. The fact that it doesn’t require wiring is a bonus for some people. There are very few diseases and pests that affect bamboo, so this is a perfect plant for those with browner thumbs. Bamboo bonsai are almost always displayed in a forest mode.
There are a large number of bamboos suitable for bonsai such as the species from the Sasa, Pseudosasa, Arundinaria and Phyllostachys genus. All are clump forming and they produce rhizomes that coil in the bottom of the pot and push up through the soil. The easiest to grow as bonsai are the dwarf versions, which can be started from outside plantings. Heavenly or Sacred Bamboo (Nandina domestica) is widely sold for bonsai, but is a shrub rather than a true bamboo.
Bamboo requires the same conditions as any houseplant – well-drained, good soil and sufficient light. They cannot grow in standing water. Potted plants should be fertilized every two weeks in the Spring and given high nitrogen fertilizer in late Spring/Summer to promote stem propagation. A high-nitrogen, low potash fertilizer, such as 30-10-10 is preferred. Bamboo bonsai should be repotted every one to two years in a basic soil mixture. You must leave sufficient space between the root ends and the container walls, so a wider, flatter pot is preferred. When the bamboo becomes root-bound, you must either re-pot into a larger container or must trim back the roots. Not surprisingly, the running types are more difficult to control than the clump types. Bamboo bonsai are best displayed in shallow light colored glazed oval or round pots.
In early summer, all the leaves should be removed so that smaller leaves will grow back. For thicker caned plants, decreasing the amount of water and sunlight can control growth. Temperate bamboos require a dormant period, as do most bonsai trees (exception are tropicals). Also, watering depends on soil drainage and the ability of the plant to absorb water. Over-watering can lead to root rot. Although bamboo is easy to grow, it is not fool proof.
If you have any thoughts of growing bamboo outside of a pot, please think again. Bamboo in the ground is considered a very invasive plant. Rhizome propagation can only be stopped by building impenetrable barriers below ground, and making sure that the spreading roots cannot find any cracks or openings to penetrate. One of our club members planted bamboo in his yard many years ago, and it quickly spread all over his and into his neighbor’s yard.
If you are already growing one of these fascinating plants, please share your knowledge and expertise with club members. You also could bring one of your bamboo bonsai to one of our monthly meetings to show our newer members.