Bambusa - Bamboo: Planting and Growing

Botany and description

Bambusas are large bamboos whose stems can reach over 20 m in height in their natural habitat. Bambusas belong to the Poaceae family, formerly known as “grasses”, and more specifically to the Bambusoideae subfamily, which includes all bamboos. The Bambusa genus now comprises around 120 species, mainly found in tropical and subtropical Asia. The name “bambusa” is a Latinised form of the Malay word “bambú“.

Bambusa arundinacea botanical plate, circa 1800

Among the many species, notable examples include Bambusa arundinaceae, whose canes can reach 40 m in height; Bambousa vulgaris or Common Bamboo from China, naturalised on nearly every continent; and Bambusa multiplex (syn: Bambusa glaucescens), more compact (no more than 9 m tall) and better suited to our gardens.

Bambusas form a bushy, dense and compact clump at the base, spreading upwards. The young shoots, or turions, grey-blue to light green in colour, emerge in summer, reach ripeness in autumn and develop their leafy branches the following spring.

This type of bamboo produces strong, woody and hollow canes, sometimes several metres long. In Asia, these canes are used in construction: fences, pipes, scaffolding… The stems, or canes or culms, consist of stacked hollow tubes partitioned at intervals by nodes, and often arch in their upper section. The culms are upright stems, varying in diameter depending on the species, green in colour, covered with a fine bloom that gives them a slightly bluish appearance. Over time, the canes take on a more beige to brown hue, even yellowish in the sun.

From left to right: Bambusa multiplex ‘Alphonse Karr’ – habit and close-up of culms, Bambusa multiplex (© Forest and Kim Starr), and bottom right Bambusa tulda

In Bambusas, each node has numerous branchings, flexible branchlets bearing dense linear leaves. The foliage on the culms is evergreen and mainly concentrated towards the top of the canes. The leaves are lanceolate and tapered at the tip. They are generally light green on the upper side, with a silvery-grey underside.

As with all bamboos, the flowers, pseudo-spikelets, are insignificant and hidden by the foliage. They appear intermittently in fine, arching panicles. Generally speaking, flowering is very rare. The development of an inflorescence leads to the death of the plant, with the culms withering and dying after flowering.

Bambusas produce short-internoded, non-running rootstocks. They are therefore far less invasive than other types of bamboo: these are known as cespitose bamboos. The clump of Bambusas spreads slowly, never thinning at the centre.

This non-running bamboo, very dense in stems and evergreen foliage, is perfect for creating a small hedge or a beautiful green screen in mild climates. It also makes a striking feature as a standalone clump or integrated into a shrub border. Grown in pots, this is the bamboo to choose for decorating a conservatory or large patio.

Our most beautiful varieties

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Planting Bambusa

Where to plant?

Given their limited hardiness (-7°C), Bambusas are best grown in pots in conservatories, orangeries, or in the ground in milder regions such as the south-western coastline.

Bambusas prefer partial shade, though they tolerate sun, provided it is not scorching, as well as deeper shade. However, avoid overly dry exposures, as these bamboos dislike arid conditions.

The soil should be rich and humus-bearing, remaining moist, ideally low in lime (neutral to acidic). If needed, you can replace your garden soil with a good horticultural compost.

When to plant?

In theory, container-grown bamboos can be planted year-round, except during frost.

Ideally, plant after peak summer heat, from late August to October. This allows the Bambusa to establish a strong root system before winter.

How to plant?

As a reminder: Bambusas are non-running bamboos, known as cespitose, so installing a root barrier at planting is unnecessary.

In the ground

For fast-growing varieties like Bambusas, account for their mature height and spread. A common rule is to multiply the mature height by 3 to determine the ideal planting area, ensuring the bamboo has ample space.

Example: for a Bambusa multiplex reaching around 6 metres tall, allocate an ideal area of 18 m².

• Soak the root ball in a bucket of water for a few minutes to rehydrate it;
• Dig a hole twice as deep and twice as wide as the root ball using a spade;
• Place the root ball in the centre and backfill with garden soil mixed with planting compost (special planting compost), well-rotted compost, or manure;
• Apply a 6–8 cm thick mulch (straw, dried grass, flax pale, shredded miscanthus…) to retain moisture;
• Water thoroughly to ensure root hydration and eliminate air pockets.

Please note: for hedging or screening, space Bambusa multiplex plants 1 metre apart.

In pots

Bambusas can be grown in pots, provided watering is carefully monitored. Place the pot in non-scorching sun or partial shade, sheltered from draughts.

• Choose a large container (minimum 50 cm diameter and depth, ~40 litres) with drainage holes;
• Layer gravel or clay pebbles at the base;
• Fill with a rich, well-draining mix of compost, compost, and garden soil;
• Water generously;
• Apply mulch to retain moisture.

Maintenance and pruning

Watering

Bamboo requires plenty of water to establish and grow. Water generously when planting and then very regularly during the first two years of cultivation, especially in summer and when the soil is very dry. Don’t forget to apply mulch to keep the soil cool. Over time, however, bamboos “mulch themselves” thanks to their dry leaves, which decompose very slowly.

Potted specimens require even more careful monitoring of watering: do not let the soil dry out too much between waterings. Bambusas can drink up to 5 litres per day during hot spells.

Maintenance

Bamboos thrive in fertile soil. Each spring, an application of compost at the base of the canes will be beneficial. For bamboos grown in pots or containers, a special bamboo fertiliser, rich in nitrogen, can be applied twice a year.

If the leaves of bambusas start to yellow, this may indicate excess lime in the soil. In this case, adding a little ericaceous compost to the surface or a pine needle mulch should solve the problem.

Pruning

Pruning is not essential, but bamboo multiplex tolerates it quite well. You can prune with shears around August-September to shape them or limit their growth. You can also remove dry canes (they can be used as stakes or to create decorative fencing).

Every year, cut back dry, weak or obstructive culms at the base. None of these pruned canes will regrow, but this maintenance pruning will allow the plant to develop entirely new foliage that is denser. The appearance of the bamboo will be greatly improved.

Diseases and Pests

Bamboos are resistant to most diseases and parasites. However, they can become vulnerable when weakened by excess water or a lack of nutrients.

When the weather is hot and humid, bamboos grown in pots are sometimes prone to attacks by farinose scale insects, which feed on the sap and leave white farinose or cottony clusters on the plant. The leaves turn yellow and fall off, which can lead to the death of the plant in severe infestations. Spraying a mixture of vegetable oil (rapeseed or olive oil), 90° alcohol and black soap can suffocate them.

Red spider mites can also cause yellowing and drying of potted bamboo leaves, which eventually fall off. In this case, there are various eco-friendly solutions presented in the advice sheet Red Spider Mite: Identification and Treatment.

→ Want to learn more about bamboo diseases and parasites? Read our advice sheet Bamboo Diseases and Parasites

Bambusa multiplex (© Dinesh Vale)

Propagation

Bamboo propagation is generally carried out in spring, during March-April, by dividing clumps that are at least three years old. The operation is performed when the soil is sufficiently moist, which makes the process easier.

Dividing clumps:

• Using a sharp spade, take a good-sized rootball from a clump with at least 3 to 5 culms at the edge of the main rootball;
• Shorten the culms by 1/3 of their length, always keeping some foliage, otherwise the rootballs won’t recover;
• Plant the rootball in a hole enriched with good compost;
• Backfill with the excavated soil, firm down and mulch;
• Water thoroughly to reduce air pockets between the soil and the rootstocks, then keep the soil moist, but never waterlogged;
• Spray regularly with non-calcareous water on the leaf in dry or windy weather, in the evening or morning. This will prevent the leaf from drying out and ensure good recovery.

Please note: once removed, large bamboos regrow at their juvenile stage. The new culms that emerge will then be smaller in size and diameter. It will take several years before they reach the dimensions of the parent plant.

Association

Bambusas are exotic bamboos, originating from the warm and humid regions of Asia. Ideally, one would artificially recreate a piece of subtropical forest (Asian or otherwise), in a container in colder regions or in the ground, in a sheltered and semi-shaded spot in milder areas.

Pair a Bambusa multiplex ‘Alphonse Karr’ with a Schefflera taiwaniana, a bush related to our indoor scheffleras but far more hardy (-10°C). For perennials, consider the impressive Strelitzia nicolai or White Bird of Paradise (a little nod to Michel Berger) to add volume and striking flowering. It must absolutely be brought into a cold greenhouse during winter.

Large, broad leaves always bring an exotic touch, while also creating contrast with the bamboo’s fine foliage: a Colocasia esculenta ‘Black Magic’ and its botanical cousin an Alocasia macrorrhiza or Elephant Ear.

Bambusa multiplex ‘Alphonse Karr’, Schefflera taiwaniana, Colocasia esculenta ‘Black Magic’, Colocasia macrorrhiza and Strelitzia nicolai.