A quick guide to clumping and running bamboos

One of the most wonderful and most exasperating things about bamboos – and indeed many other plants – is that they vary so much and so unpredictably. The answer to almost any question I am asked about bamboo begins, “Well it depends, but generally…” With that in mind, there are not always hard and fast answers to how a bamboo will behave, but let’s generalise a bit.

Bamboos have different rhizome structures which dictate their growth patterns. Broadly speaking they can be divided into clump formers and runners. Clump-forming bamboos send out new rhizomes which turn up to become new culms. Runners send out rhizomes which send up new culms along their length and continue on. Clumping bamboos therefore send up new culms around the edges of the clump, expanding slowly and evenly.

Typical, closely packed culms of clump-forming Fargesia rufa

Typical, closely packed culms of clump-forming Fargesia rufa

Runners can send up new culms at quite a distance from the main clump, expanding rapidly and unpredictably. However, clump forming does not necessarily mean small! While typical clumpers (e.g. Fargesia) send up new culms very close to the clump, some (e.g. Yushania and Chusquea) have rhizomes with a long ‘neck’ which can grow outward 30cm or so before turning up into a culm. These can form a large, relatively open clump very quickly.

Chusquea gigantean, a 'long-necked' clumper and a real giant.

Chusquea gigantea, a ‘long-necked’ clumper and a real giant.

Other clump formers can fountain outwards from a tightly clumped base, requiring space to appreciate their form. The foliage of such a bamboo may easily be four times the width of the base.

Fargesia rufa, a clumping bamboo which forms a mushroom of foliage.

Fargesia rufa, a clumping bamboo which forms a mushroom of foliage.

Running bamboos are harder to generalise about. Some (Sasa and Chimonobambusa most notably) are rampant and aggressively spreading. A few are very reluctant to spread or even bulk up (some of the rarer Phyllostachys bambusoides varieties, for example  – which is why they are rare). Most are somewhere in between. Unfortunately, it’s impossible to say exactly where in that range a given plant will be in a given garden situation. Some people have found that their bamboos are more prone to wander in dry soil; the theory is that they spread in search of moisture. Several plants in my garden have done the opposite, spreading rapidly in rich soil with plenty of moisture.

Widely spaced culms of Phyllostachys bambusoides 'Castillonis Inversa' a gently 'running' bamboo

Widely spaced culms of Phyllostachys bambusoides ‘Castillonis Inversa’, which might be called a ‘gently running’ bamboo

A plant of Phyllostachys vivax ‘Aureocaulis’, for example, has run in almost a straight line in both directions from the original planting. In four years it has spread from a five litre pot to a five metre wide plant. As it is a giant timber bamboo I was not expecting it to be compact, so it has plenty of room in the middle of the garden, well away from my neighbours.

Phyllostachys nigra, the black bamboo, is notoriously variable in habit. This may in part be due to the number of different clones available. P. nigra was one of the earliest bamboos introduced to the U.K. in 1823 and is still one of the most popular and most widely available. Some plants remain in a tight clump whilst others spread quickly. If you plant this bamboo, it might be wise to put in a partial root barrier or at least keep a close eye on it.

One of the myths that I often hear about bamboo is that all bamboos will run eventually. This simply isn’t true. A clump forming bamboo does not have the capacity to send out long runners. However big it gets it will not suddenly pop up elsewhere in the garden. What is true, however, is that all running bamboos do have this capacity. Many of those available will stay in a well-behaved clump. Some may, after many years in the ground, send out a single runner which is easily dealt with. Many others will wander if allowed to but can be kept in check fairly easily. And some should really not be planted in the ground at all, unless you have acres which you would be happy to see invaded.

Phyllostachys aurea 'Koi'

Phyllostachys aurea ‘Koi’

Just to demonstrate the range of ‘running’ bamboos, the plant above has been in the ground as long as the five metre wide P. vivax ‘Aureocaulis’. It has spread perhaps six inches in that time, and remains the tightest clump of any of the forty odd species I have planted out, including the clump-formers.

Bearing in mind the huge range of bamboos available in the UK, with a little research and perhaps some input from a specialist nursery, it should be possible to find a suitable bamboo for almost any garden situation.

1 Comment (+add yours?)

  1. Trackback: Using bamboo for screening | The Asian Garden U.K.

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