Buying A Bamboo Plant
Bamboo plants are offered for sale in containers in nurseries and garden centers and one can therefore, in theory, plant them throughout the year. However, a bamboo has a better chance of survival and developing it’s roots during its first winter without damage if planted in the first half of the year. The reason for this is because each bamboo plant’s rhizome has a tremendous amount of reserve in it which allows new culm growth even before new roots are established.
So if one were to plant in their above-ground growth period in spring and summer, the rhizomes begin to grow and to develop roots in June and July. If the plant is already planted in its desired position at this stage it can become well established in the ground before winter.
New root growth guarantees adequate moisture supply during the following winter. The plants will be better able to withstand cold and drying winds. Bamboos planted out in autumn look more decorative, since they have last spring’s culms. Most bamboos have a resting period from late summer to spring and will not usually produce fresh rhizomes in the autumn. Bamboos planted in the autumn therefore need close attention during the winter and must be watered to prevent drying and, in cold climates, protected from frosts. They should not be compared with other woody plants that can be planted in autumn to root vigorously in the spring. In most species – the culm develops first, followed by growth of the rhizomes.
Before you buy a bamboo plant there are two things you should look out for:
- It is difficult to see the rhizome to check whether it is really intact and has healthy buds – a requirement for healthy growth in all bamboos.
- Secondly, a container plant is not always what it appears to be. For example, a few years ago beautiful Mediterranean-grown Phyllostachys aurea was on offer. It later became clear that these had been taken from old, naturalised stands and 80 per cent made no further growth. It is therefore best to buy bamboos from a reputable grower, if possible from one specializing in bamboos and propagating their own ‘young’ plants.
- It is important to buy a healthy plant that has already developed young rhizomes. It is only in the clump-forming gen- era, such as Sinarundinaria, that the aerial parts of the plant can tell you about its overall quality and vitality. Sometimes a container plant will have only one or two culms, but many rhizomes, and such a plant will develop very well in the garden. One often sees a container plant offered with both older, thick stems, several years old, and thinner, year-old stems. Such a plant will have been taken by dividing up a large bamboo plant. The thicker stems are those that grew out of the whole rhizome, whereas the thinner ones have grown up from the new rhizomes put out after division of the original plant. As long as there are plenty of fresh culms, such a plant should be perfectly satisfactory. One can tell the age from the number of branches as well as from the size of the culms. The older the plant, the more branching there is. As a rule, try to buy bamboo plants that are reasonably young, with well developed rhizomes and young culms. Large, old bamboos sometimes do not develop any better than young ones after planting.
The position for a bamboo should be chosen primarily for its visual effect. It should be decorative and harmonize with the other plants. However, it is important not to forget the plant’s requirements. Bamboos are very sensitive to climate and water regime. Many species like full sun, whilst others prefer shade or semi-shade. Ground cover species such as Sasa, Sasaella and Pleioblastus can even tolerate deep shade. If no attention is paid to these requirements then disap- pointment is inevitable. An attractive Phyllostachys on a terrace in a shady, cool corner might look particularly decorative but will soon lose its looks and fail to put out fresh culms because it is not warm enough. Sasa species are ideal as ground cover but can become leggy and unattractive if planted in full sunlight. In their native countries and in oceanic cli- mates these species can tolerate hotter sun because the air humidity is higher. In a dry warm climate, drought damage can set in, the plants becoming yellow and eventually dying off. No bamboo likes a strong wind and the site must be selected with this fact in mind. Bamboos are thirsty plants and dry out quickly in the wind. They do excellently when grown in protected positions such as against a wall, in a corner or in a courtyard, where a wall stores the heat of the day and continues to release it in the evening, effectively producing a warmer climate. Bamboos often grow with tropical luxuriance in sheltered yards in cities. Here they are protected from wind and surrounded by walls that give out warmth, and they are not subjected to the extremes of winter cold. Bamboos, like all plants, are strongly influenced by their microclimate. They do well in courtyards or in a garden with a surrounding hedge. Several species are suitable as hedge plants but you do not need to worry about the wind if the hedge itself is bamboo. Their thick foliage protects them from drying out.
Even those species that like full sun in summer need to be provided with some shade in winter. Winter sun combined with frost is bad for bamboos, as for all evergreens. Whenever possible plant bamboos so that the low winter sun creates at least partial shade, for instance by a tree. Even if the tree is leafless, its branches and twigs will provide sufficient shade to prevent damage to the bamboo. When planting bamboos do not forget that they can grow quite large, in width as well as height. An individual plant such as Sinarundinaria can easily grow to a diameter of more than two metres (six feet) in a few years and this should be borne in mind when selecting the site.
For invasive species one must also consider the underground growth potential. A strongly rampant bamboo in the middle of a lawn is not exactly what every gardener dreams of, nor does one usually want bamboos springing up in every flower bed. If you have a garden pond you need to ensure that the rhizome tips do not bore through the lining. This dan- ger can be diminished by using a lining material thicker than 0.5 mm ( in.). Lastly, do not forget that your neighbour might not want bamboos spreading into his garden!
Picking The Perfect Soil
Bamboos are not particularly fussy about soil type. In very heavy soils or in pure sand they do not grow as well, but soils can always be improved. However they do dislike soggy soil. Take care, therefore, that you do not plant bamboos near to the water table, nor in soils where the water flow is restricted. One often finds, particularly in new housing developments, that the gardens consist of just a thin layer of soil on top of a layer of heavy soil that has been compacted by building machinery. Rainwater collects in such soil and bamboos dislike these conditions. The rhizomes rot and the plants die. A humus-rich layer of soil 30–50 cm (12–20 in.) deep over loamy soil is ideal but not always available. One therefore often has to do some soil preparation to create optimal conditions for bamboos. If the soil is very porous, bamboos must be watered regularly because they take up a lot of water. Like all shallow- rooted species and all grasses bamboo has a rapid water metabolism. Where the soil is very compacted, for example by building machinery, it has to be loosened up, usually by deep digging to break up the dense layers. This goes not just for bamboos, but for all other large plants.
If you want to plant bamboo alongside water, where it looks marvellous, make sure that the bank is at least 30 cm (12 in.) higher than the normal water level of the stream or pond. How to plant When you have purchased container plants from a nursery and chosen the site with care it is time to move on to the ac- tual planting, which is simplicity itself. Dig a hole slightly wider than the container and see whether further digging is needed to improve drainage. Now remove the plastic container prior to planting. In very light soil plant the bamboo slightly deeper than it was in the container and cover the surface with light garden soil. This delays for a few weeks the rhizomes pushing up to the light and forming culms. On the other hand, if your soil is relatively heavy, you should plant the bamboo about as deep as it was in the container. Bamboos grow larger and more powerfully in their native sites, and there new rhizomes can push up through thick layers of soil. However, one cannot depend upon this kind of growth with cultivated garden bamboos.
When transplanting a bamboo from a container to the garden make sure it is planted no deeper than it grew when in the pot, unless you are putting it in very light soil, in which case it can be planted a little deeper. Put a layer of manure be- neath the plant and mulch the surface to reduce evaporation. Invasive species can be held in check by concrete slabs or by a wall
After planting, water well and firm down the soil. When planting in spring, however, be careful not to tread on any fresh rhizomes that may have sprouted a few centimetres above the surface. Whatever the season, the soil should be mulched to reduce water loss and promote growth. Well-rotted compost is suitable, or fallen leaves from trees and bushes (but not sweet chestnut leaves or those from nut trees, since these contain a lot of tannic acid). Peat is not suitable because it tends to draw the water out of the soil and so has the opposite effect. If you use freshly cut grass, mix it with chopped-up twigs otherwise it will get too hot as it rots. Sawdust, hay and straw are also useful. Let the mulch material settle into the plant from above to a depth of 20 cm (8 in.). The procedure is similar for planting in a wooden tub or stoneware con- tainer, for example. Make sure that the container is large enough to allow for sufficient root development for the plant height desired. If it is too small you may have to re-pot the plant the following year, otherwise it will outgrow the pot and begin to starve because it will have developed too many culms. It is particularly important that the container has suffi- ciently large drainage holes.
Occasionally you might wish to move a well-established bamboo – perhaps because the site is not after all appropriate, or because you have rearranged the garden, or, as occasionally happens, you are moving house and want to take it with you. However remember that moving a bamboo plant weakens it. The rhizomes and fine roots are always damaged, even if the utmost care is taken. Therefore one needs to choose the best time for the transfer, and the best time is either short- ly before the new growth begins, or immediately after the new culms have completed their growth. This is the moment before the rhizome starts its own growth. Rhizome growth should not be interrupted by replanting or division. It is gener- ally better not to move the whole plant to the new site but to take pieces with just a few culms, or, for example with Pleioblastus, to plant pieces broken off the rhizome. This gives rise to more vigorous plants than replanting the whole bamboo. Sometimes no more new culms develop in the centre because the older rhizomes have been damaged during the transfer, and the new rhizomes develop outwards. After transplanting it helps to keep the plant in still air and shade under a sheet for about a week, and to reduce the leaf area by cutting back the side branches by one to two thirds. This is important because the developing rhizome cannot take up a lot of water from the soil. Well-developed plants often take several years to return to their original size and beauty after transplanting. However this is not always the case, and much depends upon the condition of the plant, on the species and on the precise envi- ronment of the new site.
But it is not enough simply to watch the leaves. You should try to judge how dry the soil is in the garden or container and whether and when it is necessary to water. In the case of containers especially, you need to develop sensitive finger- tips to check soil moisture. It is very easy to overdo the watering and if waterlogging sets in then the rhizomes and roots rot and the plant may die. If you are the proud owner of a bamboo hedge you can make the watering easier. Simply lay a spray pipe between the plants, or use a hose that you have punctured at regular intervals with small holes. The whole hedge can be watered thus without one having to stand and spray. Larger groups of bamboos are not so likely to suffer, because they create their own shade. Bamboos need a lot of fertilizing. In Japan valued bamboo plantations are fertilized with horse manure, which contains a very high proportion of nitrogen. If you have access to half-rotted horse or cow manure you should apply liberal quan- tities in autumn or early in the spring. Riding schools are often glad to give away manure since they have no use for it. The chance should be grabbed. If you compost fresh manure in summer it is ready for use the following spring. If it is too concentrated it will not rot, so it is a good idea to mix it with straw. Then it rots quickly and completely. If there is no animal dung available you can use fertilizers with a high nitrogen content. These also have the necessary phosphorus and potassium (NPK-fertilizers).
Silica (SiO2) is just as important for bamboos as nitrogen. Bamboo plants contain a large amount of silica and this must be supplied continuously. When growing in large groves bamboos get sufficient silica naturally by recycling it from their shed leaves, which rot on the soil below and release it. One should therefore let fallen leaves accumulate beneath individual bamboo plants. Rake together those that have fallen on the soil around the plants and place these under the plants as well. This should give the bamboos enough silica, but it is a good idea to supplement this in the first few years with SiO2. This can be supplied in organic form as Horsetail extract. Horsetail contains even more silica than bamboo, especially in summer when fully grown. The extract must be boiled for about 30 minutes after soaking the plants for 24 hours. It is then mixed in a ratio of 1:5 with water before being applied to the bamboos. It smells very unpleasant so it is preferable where possible simply to mulch with Horsetail, although make sure it is dead first! Bentonite, a silica-rich clay mineral, is very good for supplying bamboo with this important nutrient. It is spread on the soil and washed down by the rain. If you do not want to be bothered with organic fertilizers, commercial lawn or garden fertilizers can be used instead. Apply 150 g (5 oz) mineral fertilizer each year to every one square metre (square yard) of soil. Be careful not to allow salt accumulation in the soil. Bamboo is very sensitive to salt in the soil and if too much fertilizer is applied this is a danger. The soil should be inspected regularly under valuable bamboo stands. There are mineral fertilizers with reduced salt available. Another useful fertilizer is this: mix 4 parts ammonium sulphate, 1 part superphosphate and 1 part potassium sulphate. Apply this mixture three times at two-week intervals before the start of the growth season at the end of April until the end of May, as above, 150g/sq.m. (5 oz/yd²).
In the case of a bamboo hedge there is another reason for cutting out the old growth. A bamboo hedge should provide a screen and windbreak and therefore needs to be thick. Since relatively large species such as Sinarundinaria, Phyllostachys and Semiarundinaria are used for hedges, over the years they develop thick, leafy crowns but the culms below are rela- tively free of foliage. They therefore begin to lose their effectiveness as a shield, and a tall hedge will start to cast too large a shadow in a small garden. A thicker, not quite so tall hedge is better for most gardens. This is not arrived at by conven- tional pruning such as might be used for, say, a privet hedge. With bamboo all the older growth must be removed every year. This reduces the leaf area of the plant and in turn the photosynthetic build-up of new plant tissue. The plant devel- ops only medium-sized stems and its growth is naturally checked. There is another rather more work-intensive way to keep a bamboo hedge short and thick. By pruning individual culms it is possible to get them to put out more branches and leaves. The culm should only be cut in its upper third after it has developed all its branches. If it is cut earlier it may die back. One disadvantage of this method is that the growth character of the bamboo is lost and one simply creates a thick green wall, lacking any particular beauty. Before pruning a bamboo hedge in such drastic fashion one should wait to see how the plant develops. For example, if you have enough patience a Sinarundinaria hedge may provide enough shelter, even though the leaves develop mostly at the top of the culms. These species bend over and therefore give extra thickness to the hedge. It would therefore be a great shame to prune a Sinarun- dinaria hedge drastically before it is at least ten years old. Sinarundinaria occasionally grows too thick as an individual plant and loses its attractive shape. Then you need to take more radical steps and remove all culms older than two years, very difficult in the case of a large, thick plant.
An alternative to concrete is thick plastic. This can be curved to give a natural border between the bamboo and other beds. Bamboos can be completely surrounded by this material. If the barrier is buried 60–100 cm 2–3 ft) deep in the soil, and lawn or flowers grown on top it is completely hid- den. The joins, however, must be tight otherwise the rhizomes will penetrate the gaps. If you want to have bamboo in a flower bed or between other plants, plant it in a large pot or in a plastic barrel sunk into the soil. Make sure that you have a good water supply and effective drainage beneath the barrel. Tall leptomorph genera like Phyllostachys, Semiarundinaria, Pseudosasa, Bashania or Brachystachyum do not usually send out rhizomes deeper than about 50 cm (20 in.). Again, bar- riers made of plastic are useful, as are concrete rings which can be purchased at building suppliers. All barriers should be at least a metre (three feet) in diameter, otherwise there is the danger that the plants will dry out too quickly as they no longer have long rhizomes bringing in supplies from fur- ther afield. Another possibility is to have an undergrowth of robust perennials or shrubs, but make sure they do not get the upper hand. Both the undergrowth and bamboos must be regularly thinned and pruned to prevent them growing into each other. If you already have bamboos in your garden with no mechanical barriers they have to be kept in check by other means. This can be done above the ground. The new shoots can be cut off by mow- ing early in the year, at least once a week, otherwise new shoots will appear for several weeks. (In the case of Phyllostachys this is a real shame, because the shoots are a delicacy.) Alternatively, the shoots can be cut off at the rhizome with a sharp knife or secateurs. Destroying the shoots only im- proves the appearance, however, and the rhizomes continue to grow underground. These have to be capped when they grow in the wrong directions. With the larger-growing genera, whose rhizomes are not so deep, this is relatively simple; they can be severed with sharp scissors and do not have to be dug up. If it is a young rhizome it will die, since it is dependent upon the main plant. If it has been spreading for several years the rhizome will have to be dug out. If you are careful to leave a few culms on the rhizome it can be transplanted to another part of the garden, or given to a neighbour. With the stronger-growing short species it is more difficult to get rid of the rhizomes. They have to be completely removed. If you have to dig them out it is a good idea to put in some kind of barrier, so you do not have to repeat this unpleasant task.
Bamboos in the winter
Do not cover the plant with a plastic sheet. Firstly, plastic sheeting is too thin to protect the plant from hard frosts, and secondly, when the sun shines, the heat produced would be even more dam- aging than the frost. Valuable bamboo plants or newly planted ones may be covered for a very few days in blistered plastic sheeting, but only when the winter sun is not shining. Experiments using a fleece tent as a snow substitute have proved successful in recent winters. It is best, however, to let nature take its course. As long as the plants have been well mulched the rhizomes will not be damaged. The culms and leaves can tolerate a great deal of frost as long as they have not been weakened by excessive applications of fertilizer in summer and autumn. Even when the culms and leaves are completely frozen strong plants will retain sufficient reserves in their rhizomes to enable new culms to be produced. It has recently been shown that bamboos become deciduous in really hard winters, dropping all their leaves and growing new ones in the spring. Usually, not all the culms will be killed by the frost, even though a bamboo plant may look pale after a hard winter, and its leaves yellow. The buds from which new branches and leaves grow are more resistant than the leaves and it is astonishing to see how a bamboo that seemed moribund starts to put out fresh growth in May, both from the dead-looking culms and from the rhizomes. It is not a good idea to cut back the culms simply to improve the appearance of a bamboo that has overwintered, and sustained drought damage. If this is done, young plants in particular will regen- erate only very poorly in the following year. Some gardeners remove the dry leaves after a hard win- ter. These straw-yellow leaves are attached quite firmly to their sheaths and removing them rips away the sheath as well so that the buds are no longer protected from drying out. It is best, there- fore, to leave all the leaves in place on the culms and branches until the new branches have started to grow and the rhizome has begun to sprout. It is also important to make sure the plant has suffi- cient water, even when it seems to be completely lifeless. Do not cut out the dead culms until the plant has begun its new growth. In a mild winter with short frosts and snow, sufficient humidity and precipitation, there is no need to do anything to the bamboos, just enjoy them, as long as the soil is not frozen.
There are two ways to propagate temperate bamboos: generative propagation with seeds, and vege- tative propagation using sections of rhizome, with or without culms. Seeds are not often available in Europe and collectors usually get these from overseas. However, when a bamboo flowers and produces seeds it can sometimes regenerate via the seeds. If you have a flowering bamboo (Pseudosasa japonica has flowered in our garden for several years) you can raise seedlings from it, and this is an interesting process. After ripening, put the seed in a pot with nor- mal garden soil, mixed with a little peat. The seeds can be stored for only a couple of weeks before they lose their viability. Cover the pot with glass or plastic. This promotes better germination by maintaining an even temperature and humidity. With luck the seeds will sprout in two to six weeks, producing a tiny bamboo shoot that looks just like a grass stem. Keep it warm and damp, ideally in- doors or in a greenhouse. Be very careful when watering because the tiny roots rot easily. It takes about three years to grow in to a small bamboo plant that is ready for planting out.
Another form of division is not to cut up the entire plant, but to grow a young plant from just a piece of rhizome. You must select the right time of year for this operation too. The best time is dur- ing the development of the buds in the rhizome, before the new culms grow. This stage is at dif- ferent times of year according to the species, the climate and nourishment. One cannot therefore generalize, but each gardener must observe the individual plants carefully to establish the right mo- ment. Rhizome pieces will only send out new culms if they contain active young tissue. Clump forming bamboo species with pachymorphic rhizomes are propagated in the following way. Part of the plant is cut off at the rhizome neck, the narrow point of attachment. Such a wound rots quickly, but only as far as the active tissue. Such bamboos can only be propagated using rhi- zomes that are up to a year old, since only these can send out the side rhizomes which are essential for further development. The year-old rhizomes can be identified by the young roots they carry. Older rhizomes are not able to grow new rhizome. On the young rhizome there must be a culm, with branches and leaves, although evaporation can be reduced by cutting back to the first few in- ternodes, as long as at least two branches are left on the culm. If you remove the culm completely the rhizome does not develop its roots as successfully. To propagate species with leptomorphic rhizomes you need a piece of rhizome at least 30 cm (12 in.) long with several nodes, and it should be one or two years old. There is a good reason why one should not use much older rhizome pieces, and this is connected with the development of rhizome and culm. In the first year the rhizome grows out horizontally, growing a bud at each node. In the second year the rhizome continues to grow horizontally, with new bamboo growth at the buds. By using one- or two-year-old rhizomes one ensures that the buds are already developed so that one does not need to wait too long before culms appear above ground. It is best of all to use a piece of rhizome that already has one or two culms on it, as well as rhizome growth from the previous year and a piece of rhizome should have buds clearly visible on at least three of its nodes. Within a few weeks of planting one or two culms should be visible, depending on the amount of reserves stored in the rhizome. By using a piece of rhizome with one or more culms you can reduce the propa- gation time by a year. On the other hand rhizomes with culms, branches and leaves need more feeding and watering than a culmless rhizome. If it is not looked after well such a rhizome can be so exhausted by the culm that it has difficulty producing culms, buds and fresh rhizome in the fol- lowing year.
A bamboo hedge is both attractive and useful. It provides a screen and windbreak for the garden and is easy to maintain, and because it is evergreen it has a number of advantages over most hedges. It is attractive throughout the year and continues to provide the garden or terrace with pro- tection from the wind when it is most needed. A bamboo hedge creates a favourable microclimate from which all other plants will profit. In England Pseudosasa japonica is particularly common as a hedge plant. It grows very thick and because it has relatively broad leaves it is very effective as a windbreak. In France Semiarundinaria fastuosa is commoner. This is planted between streets and houses because it provides a barrier against noise and dirt. Such hedges are very straight and strong but have their own appeal. Sinarundinaria can also make a delightful hedge and in this case it is not just the leaves, but also the many culms, that provide the protection. Birds like to nest in bamboo hedges and use fallen leaves and sheaths for nest-building; cats find it very difficult to clamber up the culms to reach the nests.
The older the hedge the denser it becomes, and the closer together the young bamboos were planted the quicker it thickens up. Planting a new hedge with Phyllostachys at 1.5 m (5 ft) intervals will give an almost closed hedge, provided the planting and maintenance are carried out correctly. With some species there is a danger that after a few years the hedge will remain dense only in the upper part and this is true for Phyllostachys species. This is because the taller culms tend to put out branches and leaves at the tip. It is therefore best to keep a bamboo hedge relatively short to main- tain its screen and windbreak qualities. This is not achieved by conventional hedge pruning and the hedges would soon become unsightly if all the stems were cut back to the same height. Each culm would put out more branches but the hedge would not look very good and would be quite untyp- ical. Another method has to be used whereby the hedge is continually thinned. A proportion of the older, more unsightly culms are cut off regularly at ground level. The hedge will only keep its shape if it is regularly pruned in this way.
Monopodial species can grow very long rhizomes. If you do not want a hedge to turn into a grove the shoots that grow up outside the boundary of the hedge must be dug up (and can be eaten in the case of Phyllostachys). Alternatively they can be removed with a lawn mower. For the neighbours’ sake chop off the rhizomes with a sharp spade, or keep them in check with stone blocks or plastic, sunk at least 60 cm (2 ft) into the soil.
If you have a large garden you can allow a group of bamboos to grow into a grove and this is one of the most fascinating ways to grow bamboos. All the taller species are suitable – especially Phyl- lostachys and Semiarundinaria, Phyllostachys being the most attractive. P. aureosulcata and P. bissetii, for example, grow very upright, but the arching species also look good. The so-called ‘giant bamboo’, Phyllostachys viridis, is also suitable. In temperate latitudes this species does not grow as huge as in its native land, but it does reach 20 m (65 ft) in southern France and Italy, forming some of the most impressive bamboo groves in Europe. In areas that are not too cold P. decora, P. rubromarginata or P. viridiglaucescens are good species to plant. One has to be very patient in planning a bamboo grove because it takes about ten years to reach its full height. First put three or more plants in position, making sure there are no other trees or shrubs in the vicinity. While the grove is growing the area can be made more attractive by placing beautiful stones amongst the bamboos, and sowing annuals and biennials in between. Bushes and shrubs are not suitable because the large bamboos would compete with these and take away their light, nourishment and water. The bamboo plants grow more and more powerfully each year, until they reach their maximum height after about ten years. The taller the plant, the more strongly its rhizome spreads and the thicker its culms become. The more culms, branches and leaves it grows, the better will be its sup- ply of nutrients to the rhizome, allowing it to store more reserves, in turn sending out stronger culms. The bamboo grove develops tall culms with a dense leafy roof – just the features one strives to avoid in a bamboo hedge. However, the grove should be thinned every year. It is sufficient to re- move the four- to five-year-old culms and for this you can use the method favoured by professional bamboo planters in Asia. Mark the culms in their first year of growth using a permanent marker
pen. In this way it is always clear which culms are ready for removal. If you are familiar with bam- boos you will know from its appearance and amount of branching whether a culm is ready for cut- ting or whether it should be left for another year. When the grove is fully grown you have it, so to speak, for life. Be careful therefore that it does not take over the rest of the garden. It will grow steadily larger and take away light and nutrients from other garden plants, and for this reason the siting of a bamboo grove needs very careful thought indeed. Ground cover The low-growing bamboo genera such as Sasaella and Pleioblastus are useful for providing ground cover and indeed are often planted like lawns in Japan. Pleioblastus pygmaeus is particularly suitable, as are P. pumilis and Sasaella ramosa. Although these species grow to 80 cm (30 in.) they can be kept shorter and thicker by occasional mowing. Sasa and Sasamorpha do not spread as quickly but are good for planting under trees and large shrubs because they are shade-tolerant. Sasa veitchii is very attractive with its leaves that dry from the edges in autumn. To make a quick ground cover of low bamboos you have to plant 8 to 12 per square metre (square yard) in the spring, which is expensive. It is cheaper to start with 1 to 4 plants per square metre (square yard) and to sow summer-flowering annuals between them. After about five years the leaves will have closed the gaps, depending on the spreading capacity of the bamboo and the soil conditions. The following rule of thumb for planting ground covering bamboos may be helpful. However, bought plants do vary a lot in size. To cover 1 square metre (square yard) it takes:
|1 plant||4 to 5 years|
|3 plants||3 to 4 years|
|5–7 plants||2 to 3 years|
|8–12 plants||1 to 2 years|
Groves, hedges and ‘meadows’ of bamboo, as well as large individual plants, are particularly suit- able for open places. Bamboos require little attention and are relatively insensitive to air pollution. In Japan for example, where pollution was a big problem before the introduction of catalytic conver- tors, bamboos suffered no obvious damage; they seem to be sensitive only to salt in the soil. Bam- boos are quite at home in built-up areas and some cities have made use of this. For example, Bern University in Switzerland has large bamboo plantations lining the roads. Bamboos are increasingly planted around public buildings. Their light-green foliage ameliorates drab concrete, even in winter, and bamboos are also seen in public parks and occasionally in pedestrian precincts. Europeans and Americans are just beginning to make use of bamboo in the ways that the Japanese have done for years, particularly as street planting. The thick rhizome layer holds the plants firmly in place and there is no danger of heavy rain washing soil out on to the streets. In Japan such bamboo beds are mown every year, promoting a thick, short growth.
Bamboos on the terrace
A terrace is an excellent site for growing bamboos. Bamboo provides a splendid loose shield throughout the year for terraces in built up areas. Behind a bamboo screen one does not feel hemmed in, since the bamboo is effectively a light-green curtain which lends a special atmosphere to the terrace. The patterns of light and shade produced by the leaves, even in the slightest breeze, have moved the Chinese and Japanese for centuries to regard bamboos as ‘house art’. In Asia peo- ple are capable of meditating for hours on the shadow produced by a bamboo branch. Species with delicate foliage and attractive branches such as Phyllostachys aureosulcata, P. bissetii and P. humilis are particularly good for terraces. These species are all beautifully branched. The branches of Sinarundinaria nitida ‘Eisenach’ and ‘Nymphenburg’ hang down like green cascades. Phyllostachys bambusoides ‘Castillonis’ has a yellow culm with a green sulcus and occasionally white-striped leaves and looks very fine near the house, although it is not quite as hardy as other Phyllostachys. Growing near the house helps to protect the plant from extreme cold, strong winter sun and sharp winds.
Bamboos on the terrace are particularly welcome in winter. On the greyest of days they provide a touch of spring, and when the snow clings to the green leaves and branches, bending the culms right over, the sight is a source of pleasure and wonder. Terrace bamboos can be underplanted with flowers. However these must be species that do not need much light. Ferns can also look attractive beneath bamboo that is not too thick and busy lizzie (Impatiens) in all colours grows well and look splendid. Low-growing roses are another possibility. These go well with delicate bamboo foliage, even though they may not flower as profusely as they would in full sun.
Bamboos in the courtyard
Bamboos are particularly well suited to courtyards, or for covered spaces. The rhizomes seldom damage the flooring and if a shoot grows up from between the stones it can be removed easily, or left to grow. This can look extremely attractive. Bamboos like the protected climate of such areas and it is possible to grow species that would not flourish outdoors. However, do not forget that quite sharp frosts are possible even in courtyards. Arrangements with bamboos in courtyards look especially attractive if the bamboo is given cen- tral place in the display, possibly together with a pool and large stone, or with ferns, mosses and ivy planted underneath. If you do not want the courtyard plastered or concreted you could try a Japa- nese display, with bamboo and white gravel raked with graphic designs. Such a yard is purely deco- rative and cannot be used for general outdoor activities. When siting bamboos in a courtyard re- move some of the floor stones so that the bamboos can be planted direct into the soil. If they are planted in a trough this must be protected from frost in winter because the earth might otherwise freeze solid. Courtyard bamboos need to be watered more frequently than those outside. This is partly because the floor covering prevents the rain from soaking into the soil and partly because the walls and overhangs provide some protection from the rain. Tropical species still need to be brought indoors in winter, to a bright position.
Bamboos are beginning to be used to great effect on roofs, sites that are not normally accessible. Although green roofs cannot replace parks and gardens in built-up areas, flat roofs provide much potential space for oxygen-producing plants which can improve the climate in inner city areas. They also give flats and offices some protection from extremes of climate. In summer the plant and soil layers prevent excessive heating of the roof and the air underneath, and in winter they help to keep out the cold. Before planting up a flat roof it has first to be covered with a 1 mm thick sheet to contain the root growth and this must be of a material that will not rot. This prevents the roots from penetrating the roof and making it leak. A nylon mat ensures the necessary aeration of the roots and also lets ex- cess water run out, whilst a fleece mat on top of this prevents any of the substrate from escaping. Since soil is often too heavy to use, especially if the building has not been designed with a roof gar- den in mind, stone-wool mats are often used as a substrate. These are lightweight and easily trans- ported to the roof. However they are only available up to 20 cm (8 in.) thick, insufficient for bam- boos and shrubs, let alone small trees. Bamboos are therefore planted in special tree baskets that prevent the rhizomes from spreading out and penetrating the roof. Thus one cannot completely cover a roof with bamboos, like a lawn. The rhizomes would spread out too strongly and would sooner or later break through the protective sheet. It is also too hot, dry and windy for a bamboo ‘meadow’ on a roof site. They should therefore only be used in conjunction with other plants and in sites that are accessible for watering and fertilizing. Only reliably hardy bamboos, and other species that do not grow too large should be planted on roof sites. Trials with Sinarundinaria murielae, S. nitida, Pseudosasa japonica, Pleioblastus pumilus and other Pleioblastus species have proved successful.
Roof gardens As long as they are sufficiently strong, roofs provide a good site for creating gardens. The same ap- plies here as for courtyards and terraces. Only reliably hardy species should be used, as recom- mended in the previous section. It is commoner however to use containers on roof gardens and the following chapter should therefore be consulted as well.
Growing Bamboos in Containers
Planting and cultivation
Even if you have no garden or live in a city flat you can still grow bamboos because they make very good container plants. In theory one can grow almost all bamboos in containers, on a terrace, bal- cony, roof garden, conservatory or at a bright window inside the house. Tropical species are often used, since these can be brought inside to avoid the hard winter weather. One uses different criteria when considering container plants. Garden plants need to blend in well with others to make the overall picture, but in the case of container plants it is the individual beauty of the plant that is of prime importance. Whenever possible use species that have a particularly beautiful shape or special features such as interesting stem colours, beautiful sheath patterns or elegant foliage. All Arund- inaria species, Bambusa and some Phyllostachys species, such as P. flexuosa, P. nidularia or P. nigra are particularly attractive in containers. The drooping forms of Sinarundinaria are also very suitable. As in the case of garden bamboos, container bamboos need the right site for optimal devel- opment. Some need full sun whilst others do best in semi-shade, depending on the species and genus. Above all the container must be large enough – less than 50 litres (11 gallons) is far too small for most of the larger species. Unlike outside, where the rhizomes are free to spread, in this case they are restricted. Like other plants, bamboos become stunted if the culms and leaves are not sufficiently well nourished by the roots. A large container is therefore absolutely vital if one wants to grow a magnificent bamboo.
If you do not want the bamboo to grow too large in its container or pot – and for house and balcony plants this is desirable – it is possible to keep it small and bushy. The trick is to divide the plant, for several years running, into individual culms, each with just two or three rhizome buds. From these you get fast-growing but small young plants that can be kept in small pots. If you a well-developed bamboo in a container make sure it does not develop too many culms, otherwise the restricted
Bonsai with low-growing species There are different ways of cultivating bamboo as bonsai. The simplest method is to plant a low- growing species, such as one from the genus Pleioblastus in a shallow bonsai bowl, give it reduced fertilizer and water and remove the two-year-old growth. The shallow pot contains relatively little substrate, so the rhizome remains small and is only able to send up small culms. The water supply has to be regulated quite carefully so the plant neither dries up nor drowns. One feed during the growth period is enough for a bonsai plant and, with a small species, you can main- tain a height of about 20 cm (8 in.) It is more interesting though to use species with unusual growth, coloured leaves, thickened in- ternodes or remarkable culm colours. Examples are Bambusa ventricosa (Buddha’s belly), in which the internodes thicken up when it is grown under conditions of reduced nourishment, Phyllostachys aurea, with shortened internodes, and Chimonobambusa quadrangularis which has square culms. Others which are particularly attractive as bonsai are Bambusa vulgaris ‘Vittata’ and Phyllostachys bambusoides ‘Castillonis’, both of which have yellow culms with green stripes, Chimonobambusa marmorea with its red culms and patterned sheaths and C. m. ‘Variegata’ with white-striped leaves. In China species with a white bloom on the culms are valued in bonsai. Pseudosasa japonica, Bam- busa glaucescens and its various cultivars, and Phyllostachys humilis are also suitable. As yet we are relatively inexperienced in bonsai and until recently the number of species has also been rather lim- ited. This is, however, beginning to change and the choice of species is growing steadily. Bonsai through culm pruning In Asia they use more subtle methods to make dwarf forms of normal bamboos. With sympodial, that is clump forming species with pachymorphic rhizomes, all the culms of the young plant are cut off just before the rhizome’s growing season. This is in early summer when the culms have branched and the leaves developed. The rhizome is then planted in a shallow bowl in a mixture of soil and sand. Since the rhizome was unable to store food produced by the previous sea- son’s growth the culms produced the following year are smaller than normal and if the procedure is followed the next year the growth gets even smaller, as do the branches and leaves.
For monopodial, invasive species the method is to dig up about 30 cm (12 in.) rhizome as for propagation and plant this in soil and sand, either vertically, or better still in the shape of a bow, with the curved section (which must have buds) about 6 cm (2 in.) under the soil and each end poking out. The buds under the soil send out small rhizomes and the ends of the rhizome develop small culms with branches and leaves. Bonsai through peeling the culm The Japanese bonsai master Koichiro Ueda recommends the following method. When the shoots have grown to about 8 cm (3 in.), the culm sheaths are removed, repeatedly during the period of culm growth, from the bottom upwards. These sheaths contain growth hormone and when they are removed internode growth is halted. Removing the sheaths is tricky, and cannot be done by hand since this would damage the soft culm. It is best to use a fine sharp pair of scissors inserted between the culm and sheath. This way the sheaths can be cut into strips, from the tip towards the nodes, and then carefully removed so as not to damage the buds from which the branches and leaves will develop. Start with the lowest in- ternode and then watch the growth of the second, peeling off the sheath at the right moment. This can take up to a day, and must be repeated until the whole culm has been peeled. Bamboos also grow at night and Ueda recommends watching through the night as well, if necessary. The bare culms are very delicate and soft and need to be protected from direct sun until they are firm and have sent out their branches and leaves. Feed well in early summer and early autumn so that the resultant bonsai plant will develop a good colour and do not be too sparing with water in the early stages. In autumn transfer to an attractive bonsai bowl, which will restrict rhizome growth. If the original plant had several culms it is possible to grow a miniature bamboo grove in due course. Bonsai bamboos look best indoors, as room decoration, but even these mini bamboos should be given a spell outdoors, especially the hardy species, which benefit from a winter rest period.
Bamboo as a Raw Material
Bamboo culms removed when hedges are thinned or individual bamboos pruned are much too useful to be simply thrown away. They can be used for many purposes, although not quite as many as in their native land. There the culms are much thicker, but even the thin culms gathered from the garden can be used for all sorts of handicrafts. A single cane is a good support for a tall pot plant, or for staking herbaceous plants in the garden. Several canes can be tied together to make a trellis as a support against a wall for roses and other climbing plants. Make sure that there is a gap of 1–2 cm ( in.) between the trellis and the wall so that the plant can twine round it, and also that the hooks holding the trellis are firmly secured – climbing plants can be quite heavy after a while. A bamboo trellis also makes a good partition between balconies, or as a windbreak, with a vine, knot- grass or runner beans. Push the vertical canes into two pieces of wood with holes bored in them, one below and one secured above. The horizontal canes can then be woven between these. It is eas- ier to use freshly cut canes which are still pliable. Bamboos are also good for fences, although the canes grown in temperate climates are not thick enough for a really stable barrier. However, for decorative fences the thinner canes are ideal. The canes may be pushed into the soil in an arched pattern and tied where they cross over. This is effec- tive in keeping dogs or poultry out of vegetable or flower gardens. Many tall plants, such as sun- flowers and raspberries, can be kept upright by using bamboo canes. Set wooden posts into the soil about a metre (a yard) apart and attach horizontal bamboo canes to these by tying them together with unrottable string. The plants are then tied on to the bamboo canes. This looks much nicer than wire and is also more stable. It is not only in the garden that bamboo canes are useful. A door curtain made of bamboo and beads not only looks good, it also keeps flies out. The individual internodes should be sawn off at each side of the nodes. If they are left on they have to be drilled through, which is quite hard work. Then bamboo segments and wooden or glass beads are threaded onto strong nylon, in whatever pattern you so desire. These are secured at the top on a drilled piece of wood hung underneath the lintel. The proportion of bamboo and beads can be varied to create beautiful patterns. If a bamboo curtain is too much like hard work you might consider making a bamboo mobile for a window or door opening. Attach different length bamboo segments to a bamboo cane using nylon thread. Bamboo can be bent easily after heating, and original and attractive holders for bathroom towels or kitchen cloths can be made in this way. Bend the bamboo over a flame into a large circle and tie the ends together with coloured string, or push the thinner end inside the thicker and stick with wood glue. Hang this on a rope as a holder for hand towels. Another possibility is to stick two or three pieces of cane between two painted pieces of wood as a holder for towels and other cloths.
The above illustrates just a few of the things which can be made using the strong yet supple properties of bamboo and, with a little imagination, there are no limits to its use. Those with a knack for handicrafts will be able to make bird boxes, venetian blinds, and other intricate objects from bamboo canes. However, always bear in mind that bamboo should be handled differently from wood. Drilling If you drill a hole through bamboo, for example to thread a ribbon or to take a screw, always drill from the outside. It is also better to use a metal drill bit rather than a normal wood bit, so as not to split the bamboo. Best of all to use is a drill with a heated bit that burns through. In this way you can drill a hole in a straight line directly through the stem, in any required diameter, and it will not fray. Sawing A wood saw is not very suitable for cutting, particularly if the bamboo is thin, and it is better to use a fine hacksaw or, failing that, a very sharp knife. Splitting For some handicrafts you need split bamboo, not the complete round canes. Short sections can be cut by knocking a knife through the cane using a wooden mallet. For splitting an entire stem it is better to clamp the knife upright in a vice and to knock the stem against it with soft hammer blows. If you have an old flat iron, split bamboo canes can be ironed flat. Rest them on a smooth fire- resistant surface, heat the iron to very hot and press down hard to iron out the stems.
Bending Bamboo can be bent when cold or heated. Thin, freshly cut canes can be bent into small circles, and they keep their shape if they are held firmly in position for a few days. Narrow bamboo splits can be bent easily into circles. These can be sewn together to make chains, for use as curtains or for hanging lamps from. Thicker pieces of bamboo should be bent when warm. They become soft and pliable at about 150° C (330° F) and can be worked into almost any required shape over a gas flame or the heat of glowing charcoal. Distortion In Asia bamboos are often distorted to make them rectangular, and this can be done easily with thin culms. The shoots are made to grow through a rectangular pipe (almost like a chimney) so that the soft, growing culms take on a square shape. When it grows out of the top the shape is retained. Surface preparation Bamboo culms look very attractive without treating, especially the striped or speckled types, but they look even better when polished with hot wax. If you are not happy with the natural colour they can be etched or painted. Ferrous sulphate colours the stem black, nitric acid brown and copper sulphate green. Holding bamboo in an open flame brings out brown spots. Painting Bamboo culms can be painted, but the surface needs to be primed first, using a fine sandpaper so that the paint will adhere. Household objects are best painted with coloured inks and those for use outside with a waterproof lacquer.
If bamboos get too dry in the house or conservatory, and especially if their air is too dry, they can be attacked by red spider-mite, aphids and insects. These can be controlled using standard house plant remedies. Red spider-mite attacks when it is not only too dry but also too warm, and spreads especially quickly in centrally heated rooms. The mites are difficult to spot with the naked eye, but the damage they cause is obvious: the leaves go pale, then yellow and finally dry up. They can be treated with a special acaricide which is applied three times at ten-day intervals, but this is effective against only the larvae and adults, not against the eggs. If the treatment is not given at these inter- vals the newly hatched mites will have had chance to lay more eggs and start a new cycle. Above all, treatment has to be varied, otherwise strains develop that are resistant to the acaricide. Scale insects and aphids affect only those bamboos grown indoors or in conservatories. You often first notice scale insects by the little spots on the underside of the leaves, where each insect has sucked at the leaf, as it sits protected by its hard shield. Aphids cause the leaves to develop a shiny, waxy, sticky covering – so-called honeydew. This layer prevents the leaf from assimilating and if the plant is badly affected it can die. Aphids and scale insects are by no means easy to tackle. Watch closely so that an attack is detected early on. If caught soon enough they can be dealt with by using a solution of soap and spirit. If the plant is badly affected, however, a proprietary chemical spray should be used; making sure that the directions for use are properly followed.