11 Oct : Many bamboos are popular in cultivation as trees in gardens. There are two general patterns for the growth of bamboo: "clumping" (sympodial) and "running" (monopodial). Clumping bamboo species tend to spread slowly, as the growth pattern of the rhizomes is to simply expand the root mass gradually, similar to ornamental grasses. "Running" bamboos are aggressive in behaviourHence they need to be taken care of in cultivation.
They spread mainly through their roots and in some cases through their rhizomes. They spread widely underground and send up new culms to break through the surface. Running bamboo species are highly variable in their tendency to spread.Two main factors,soil and climate conditions control their spread. Some can send out runners of several meters a year, while others can stay in the same general area for long periods. If neglected, over time they can cause problems by moving into adjacent areas.
Bamboos seldom and unpredictably flower, and the frequency of flowering varies greatly from species to species. Once flowering takes place, a plant will decline and often die entirely. Seeds collected from a flowering may be used to rebuild a species, but flowering can also introduce unexpected alterations in the characteristics of the bamboo, so that new variants ("sports") are created instead. There are a number of interesting types of bamboo which did not exist several decades ago that have been introduced as a result of flowering. Seeds generally have a relatively short period of viability (3-12 months). Germination rates can often be improved by use of cold stratification, which involves refrigerating the seeds for a period of 4-8 weeks before planting. Although there are always a few species of bamboo in flower at any given time, collectors desiring to grow specific bamboo typically obtain their plants as divisions of already-growing plants, rather than waiting for seeds to be produced.
Once established as a grove, it is difficult to completely remove bamboo without digging up the entire network of underground rhizomes. If bamboo must be removed, an alternative to digging it up is to cut down the culms, and then repeatedly mow down new shoots as they arise, until the root system exhausts its energy supply and dies. If any leaves are allowed to photosynthesize, the bamboo survives and may continue spreading. Chemical methods involving herbicides are also used to control bamboo.
There are two main ways to prevent the spread of running bamboo into adjacent areas. The first method is rhizome pruning or "edging", which involves removing any rhizomes escaping the desired bamboo area. Pruning shears, shovels, and pickaxes are useful tools for this task. Under typical soil conditions the rhizomes are generally very close to the surface(usually within 0-3 inches, sometimes as deep as a foot). Rhizome pruning maintenance should be done at least once per year, but better is to check in the spring, summer, and fall. Some species may be deep running (beyond typical spade depth). These are much harder to control and deeper cuts will need to be made. Regular maintenance will indicate major growth directions and locations. Once the rhizomes are cut, they are typically removed; however, rhizomes take a number of months to mature and an immature, severed rhizome will usually cease growing if left in-ground. If any bamboo shoots come up outside of the bamboo area afterwards, their presence indicates the precise location of the missed rhizome. The fibrous roots that radiate from the rhizomes do not grow up to be more bamboo so if they stay in the ground, that’s not a problem.
The second way to control growth is by surrounding the plant or grove with a physical barrier. This method is very detrimental to ornamental bamboo as the bamboo within quickly becomes rootbound–showing all the signs of any unhappy, containerized plant. Symptoms include rhizomes escaping over the top, down underneath, and bursting the barrier. The bamboo within generally deteriorates in quality as fewer and fewer culms grow each year, culms live shorter periods, new culm diameter decreases, fewer leaves grow on the culms, and leaves turn yellow as the unnaturally contained rootmass quickly depletes the soil of nutrients, and curling leaves as the condensed roots cannot collect the water they need to sustain the foliage. Concrete and specially-rolled HDPE plastic are the usual materials used. Barriers usually fail sooner or later, or the bamboo within suffers greatly. Casual observation of many failed barriers has shown bursting of 60 mil HDPE in 5-6 years, and rhizomes diving underneath in as few as 3 years post install. In small areas regular maintenance is the only perfect method of controlling the spreading bamboos. Bamboo in barriers is much more difficult to remove than free-spreading bamboo. Barriers and edging are unnecessary for clump-forming bamboos. Clump-forming bamboos may eventually need to have portions removed if they get too large.