To get the most out of this article, you should understand the terms “leptomorph”, ”pachymorph”, “culm”, and “shoot”. If you haven’t already, you can read Bamboo Plant Parts I and Bamboo Plant Parts II for an explanation of those terms. You will also learn a couple of new terms in this article, “diffuse” and “caespitose”. Click on the pics for a larger image, or links to view an image, then click in the image to close it.
Running Bamboos
Virtually all of the frost hardy, timber and medium-size bamboos (30 feet and taller) have leptomorph rhizomes. These rhizomes grow laterally through the soil surface, and all have the potential to spread rapidly. In a mature grove, the culms arising from a bamboo with leptomorph rhizomes, usually have an open or diffuse habit. Because of their ability to spread rapidly and indefinitely, bamboos with leptomorph rhizomes are commonly referred to as “runners” or “running bamboos”.
Clumping Bamboos
Frost hardy bamboos with pachymorph rhizomes usually spread much slower than leptomorph bamboos, and the culms are usually arranged in a tightly spaced clump, which is known as a caespitose habit. Because of their slower spread and clumping habit, bamboos with pachymorph rhizomes are commonly referred to as “clumpers” or “clumping bamboos”. However, there are many exceptions that can be confusing to beginners.
Runners that Clump and Clumpers that Run, Oh My!
Several of the medium and timber-size bamboos that are notorious for “running” will remain in a slow-growing clump as a result of environmental stresses. Here in Shelton Washington, shade and cool summer temperatures are the most limiting factors on the big “running” bamboos I grow. For example, the Phyllostachys bambusoides ‘Allgold’ pictured below, remains in a clump of medium-size stems in the cool soils here, (a clumping runner, if you will) but grows much larger and spreads rapidly in warmer regions.
Also, most of the shrub-size bamboos, and all of the dwarf, ground cover bamboos have leptomorph rhizomes with dense culm spacing. Out of the nursery container, they start as a dense clump, but can spread rapidly into the realm of garden thugs, as pictured below.
a dwarf bamboo eating a plant bed whole
On the other hand, a few bamboos with pachymorph rhizomes have longer rhizome necks, a more open culm spacing, and can spread quite rapidly. Pictured below is a Chusquea gigantea that has covered a 10′ x 10′ area in just a few years (a running clumper, if you will).
Diffuse pachymorph
What’s it all Mean?
As a gardener, what you really need to know is how a plant will perform in a given environment. The rhizome type of a bamboo – leptomorph or pachymorph – is a broad indicator of its growth potential, but for accurate predictions you need to know which bamboo you have, and how specific growing conditions will affect it. And the absolute best way to get that information, is to talk to someone at a local, bamboo specialty nursery. You can start that journey by checking out Links Page. You can also check on bamboo forums and research individual plants online by visiting Bambooweb.info