Garden Plants

Bamboos

By Jon Ardle

Whether spreading or clump-forming, bamboos make striking garden plants useful for adding height and creating screens

'Many gardeners who are short of space may choose to plant bamboos in containers which will not only restrict their spread, but can also allow the plants to be moved around on hard surfaces.'

Bamboo adds height to the garden

Bamboos are popular plants as many of them can offer height in a narrow space – a useful tool in small gardens. They have their supporters, but this group of plants have also picked up a bad name for their wandering habit though the garden.

Runners

Bamboos grow by putting up new stems (culms) from the base of the plant in spring. In some types, such as Sasa or Pleioblastus, these can emerge a distance away from the main clump and are usually termed as ‘runners’. The spreading, running varieties are best used where there is plenty of space for them to expand and can be used on boundaries or in wilder areas of a garden.

Clump-formers

Those known as ‘clump-formers’, such as Phyllostachys or Fargesia, produce new shoots much nearer to the main plant, so they only increase in bulk slowly, but they can eventually expand to more than 1m (3ft) in diameter. To be sure that the bamboo of your choice is manageable, check with the supplier on its growth habit.

The more controlled habit of the clump-formers allows their use as discreet plants where they can be planted in numbers to form a screen or garden divider, or used individually to add a tall, columnar outline within the overall design.

Growing in containers

Many gardeners who are short of space may choose to plant bamboos in containers which will not only restrict their spread, but can also allow the plants to be moved around on hard surfaces. Containers also tend to display bamboos to a good effect, but they will need to be watered frequently and repotted regularly if the shoots quickly fill the container.

Best features

The great qualities of bamboos include an upright, narrow habit, and fine evergreen foliage that is not so dense as to cast a heavy shade, but is held on swaying stems to allow the plants to rustle in the breeze. The stems are often green, but there are varieties with coloured stems, such as the popular Phyllostachys nigra which has black stems, and Phyllostachys vivax subsp. aureocalis, which displays a green stripe on yellow stems. These stems don’t branch like trees, but will grow to a varying height from dwarf forms at less than 1m (3ft) to towering plants of over 8m (25ft) if planted in the ground.

A little light pruning is beneficial

Pruning bamboos

Where bamboos are grown as specimen plants, their appearance can be enhanced with a little light pruning. The canes can be thinned to expose individual canes rather than a dense mass of growth. As young canes appear from the base, any dead or weak canes can be cut down to the ground. If any wayward shoots are also cut down whilst they are still short, this is often enough to curb the spread of the plant. For a secondary thinning, the side shoots are trimmed from the lower levels of the canes at the point where they emerge from the cane ridges. This not only gives the canes a smooth finish, but also opens up the base of the plant and shows off the strong vertical lines.

Flowers

It is an unfortunate fact that many bamboo plants die if they come into flower. This is because the plant puts all its energy into flower growth at the expense of leaf growth so the food supply dwindles and the plant dies. A plant may be saved if the flowering stems are spotted early and cut down to the ground just leaving the leaf stems to soldier on.

Controlling a bamboo's spread

Once bamboos have established, which may take several years, new stems appear around the edges. These can be snapped off when short. Alternatively, an annual ‘chop’ around the root ball in spring will curb their vigour. It is, in fact, easy to control the spread of a bamboo growing in the border by trimming the edges of the root ball annually.

* The simplest way of controlling a clump-forming bamboo is to prune around the edges of its root ball, removing the rhizomes (underground stems) that produce the new culms. Dig a trench 30cm (12in) deep around the clump.

* If you encounter any tough rhizomes, either sever them with a sharpened spade or cut with secateurs where they emerge into the trench.

Part of the RHS Simple Steps series

* Either pull or cut the rhizomes out of the ground, or uncover them using a fork and remove. Destroy the cut sections. Alternatively, use them to propagate new bamboo plants by simply potting them up.

* Refill the trench with the excavated soil. Any new culms that appear can be snapped off at ground level; they will not regrow. Thinning out the oldest, weakest culms will encourage the bamboo to reshoot within the clump.

Look further

Bamboos and Grasses, a new book by Jon Ardle, is part of the RHS Simple Steps series published by Dorling Kindersley. The book is aimed at the beginner and has plenty of advice on how to use bamboos in different garden situations, along with their maintenance.

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