Bamboo is a remarkable and diverse plant. Most of the major continents have a native specie suited to a wide variety of conditions. Some species reach over 70′ tall while others get only 12″. Canes can be tiny toothpicks to over 12″ in diameter, they come in yellow, green, black, blue. red, mottled and speckled. Some leaves are tiny, others up to 12″, they can be a solid color or variegated, or deciduous, but most are evergreen. Yet despite this variety most of them share similar growing patterns and structure. The most important genus for landscape use in the Pacific Northwest are Phyllostachys, running; and Fargesia, clumping, these are described below.
Bamboo parts and structure
Culms and Shoots
The live stalks are called culms, or canes, though canes imply they are cut with the branches removed. The bulges are called nodes, from which the branches emerge, usually alternating from each side. Shoots are the newly emerging culms, they are often covered by culm sheathes which protect the tender new shoots. Shoots are distinct between each specie and can have a great variety of color and texture, sometimes they are the only way of differentiating between varieties. Shooting season brings the most excitement of the growing season. Each year you hope to get more, bigger shoots which grow incredibly fast, almost perceptively as you watch.
Roots and Rhizomes
The running bamboos’ rhizomes resemble the canes, though they are almost solid and the nodes are much more condensed. Even on the largest timber bamboos’ rhizomes seldom get larger than an inch in diameter, but they can be many feet long. On each rhizome node there is a bud which alternates sides, they will either become new shoots, new rhizomes, or remain dormant.
Clumping bamboos’ rhizomes resemble a J or treble hook shape. The tall vertical part is the cane, the crook is the rhizome which also has buds that will eventually turn up into new canes. The temperate Fargesia rhizome and cane network is usually only a couple to several inches wide. Feeder roots anchor into the soil providing stability, water and nutrients.
Most shoots emerge from early spring through early summer, usually starting in April through June in our climate. Species vary in timing, but all seem to be dependent on soil temperature. They come out of the ground with the same diameter as they will have at maturity, they do not get larger in subsequent years. They grow rapidly up, reaching their maximum height in about 8 weeks. They then develop branches and leaves which get denser with foliage each year. Conditions will cause variance, but typically the number of canes will double each year for the first several years, and height will increase by 3-5 feet each year.
After the shoots stop growing vertically then the rhizomes blast out laterally underground. Most Phyllostachys rhizomes will grow a finite amount each year, at the end of the season the growing tip dies back and the plant goes dormant. This growth is usually from mid summer through fall, often starting here in July and stopping in September. This is a critical aspect of the root pruning control method. Rhizomes are essentially colonizing new growing area, trying to get away from the mother plant towards more light or water. Thus the freshest, largest and most vibrant growth is often on the outward edges of a grove. This is why it is important to anticipate growth and give the plant plenty of space to get as large as you want for a functional screen or an impressive grove.