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A GUIDE TO GROWING BAMBOO FOR FOOD PRODUCTION

 

PART 3 - BAMBOO SHOOT PRODUCTION WITH TEMPERATE (RUNNING) SPECIES

SUITABLE SPECIES

There are many temperate running varieties which are suitable for shoot production. "Moso" as it is known in China and Japan, with several more or less synonymous Latin names (Phyllostachys heterocycla, P. pubescens and P. edulis) is the most commonly grown species for shoot production mainly because of the size of the shoots and consequent savings in labour that this characteristic gives per kilogram weight of harvested shoot. Other species with edible shoots include P. congesta, P. dulcis, P. elegans, P. nidularia, P. platyglossa, P. praecox and P. viridis. Square Bamboo, Chimonobambusa tetragonocalamus and a number of Pleioblastus and Sasa species also produce edible shoots, although the shoots from some of these are very slender.

SELECTION OF STOCK PLANTS

Establishing a large plantation using nursery-grown potted plants could prove expensive. Although seedlings of some species are available occasionally the supply is erratic. Most plantations are established using small stock plants or divisions.

RHIZOME CUTTINGS

Sections of vigorous rhizome about 30 cm long, taken from just behind the growing area can be either planted in nursery beds or directly into the plantation area parallel to the contour and watered in. These will produce new shoots from the viable buds and new rhizome in the next season. The ideal stock plant has one leafy culm with an attached rhizome fully capable of producing shoots. Select plants between 18 months and 2 years old. Plants over four years old are hopeless as stock plants as the buds on the rhizome will not shoot. It is not the growth of new culms above ground but the spreading of rhizomes underground that is the important consideration in the development of a strong and luxuriant grove. The most convenient size are those whose culms are between 2 and 4 cm in diameter.

Short culms are better than tall ones because they are less likely to be damaged by wind and require no support stakes, which saves labour and expense. Use young sun-hardy and vigorous culms having many branches.

Those with cracks or other injury at the junction of the culm and rhizome are worthless. Stock rhizomes should have at least five buds, for without buds shoots cannot grow. It is impossible to determine the presence of buds without digging into the ground; however, it is safe to assume that culms in their third year have live buds on their rhizomes.

WEEDS

Bamboo shoot gardens receive more sun than timber yielding groves because of the relatively wide separation of the culms. Sunlight encourages the growth of weeds which consume nutrients intended for the bamboo, shade the ground, lower soil temperature and thus retard shoot emergence.Weed using a hoe to scrape the ground surface except during the time just before shoots emerge; weeds should then be pulled up by hand. Weeds may also be controlled by growing another crop between the bamboos when the garden is new, but this should be discontinued once the garden is three years old.

FERTILISER

Bamboo is a heavy feeder so even rich soil becomes depleted after a few years if no fertiliser is added. Although fertiliser may be applied at any time of year, it is usually done after shoot harvest and again in late Summer just before mulching. Since the rhizomes are continuously active except in the coldest part of the year, it is better to apply small amounts of fertiliser several times during the year rather than a large amount all at once.

Bamboo appreciates nitrogen and potassium which are found in compost, stable manure, green manure, and wood ashes as well as in the chemical regime suggested earlier. Lime is often used both as a fertiliser and as a neutraliser for acid soil. Hay, compost, green manure and straw can simply be spread on the ground. Stable manure, ash, calcium phosphate, potassium chloride, and similar materials should be buried in small pits to avoid being washed away by rain.

MULCHING

Mulching the shoot plantation with hay, straw or composted bagasse is most important. Depending on its composition, mulch furnishes various nutrients, checks weed growth and improves soil condition. Mulch protects the shallow growing rhizomes both from Winter cold and Summer drought. Mulch should be spread during September in cool climates or during October in warm ones.

EARLY TREATMENT OF PLANTS

Plants showing poor growth and slow development should be removed. For the first 2 or 3 years most new shoots are allowed to grow into culms. Only those that grow poorly or are too close to others are removed. Sometimes bamboo rhizomes produce slender stems that grow from old rhizomes. These should be pruned off since they take up nutrition that would otherwise go to good shoots. After five years a young grove on rich soil should have about 2000 mother culms per hectare. In this year the increase by selection of new mother culms is complete. Remove about 500 of the weakest culms per hectare. The spacing of the mother culms is important. Sometimes healthy culms must be removed if they are too crowded. In year six the original, oldest culms are removed. The remaining culms are thinned to obtain uniform spacing and density of 2000 culms per hectare. The proper spacing of mother culms depends on the soil. A rich soil allows wider spacing than poor soil. Climate is also a factor. Between 1500 and 2000 mother plants per hectare is desirable, fewer for rich soil and more for poor soil.

This density is maintained for the life of the plantation. Higher density produces too many overcrowded rhizomes which reduces shoot quality. Culms are cut after they reach 7 years so that only about 500 shoots per hectare are allowed to grow into new culms each year. It is best to select these shoots from those that sprout early in the mid season of shoot production. Each must be carefully marked with the year of its emergence so that there will be no uncertainty at cutting time.

CHARACTERISTICS OF RUNNING SPECIES

Culms arise from long underground rhizomes. These spread in sinuous courses about 30 cm deep reaching maximum depths of 1 to 1.25 m. New shoots begin to emerge in September, with peak production normally in October. Culm sheaths are papery in texture and can be densely hairy and spotted. They bear bristles at the apex. Sheath blades are usually long and slender. The sheaths gradually fall as the culms grow. Culms are more or less cylindrical in their lower section but in the upper parts each internode has a broad groove on the side from which the branches emerge. The surface of the culm is smooth, green, yellowish green or yellow, and the internodes are relatively short. Nodes are ring-like. When young, culms are often covered with fine hairs and beneath each node is a band of white waxy powder. Generally, culms are stout with relatively thick walls. Usually two, but sometimes one or three, semi-cylindrical branches having prominent nodes occur directly above each upper culm node and grow alternately on opposite sides of the culm. Two to 8 lanceolate or narrow-lanceolate leaves emerge at the ends of the branchlets.

PROPAGATION

Establishing a plantation using large plants or even big divisions is very expensive. Smaller plantlets are needed. Sadly there is no sure-fire method of rapid propagation applicable to all the clumping bamboos. Most plantations are established using divisions of mature clumps. Some research work is proceeding on tissue culturing bamboos, but results are a little inconclusive except from some laboratories in India. These institutions seem to have established a reliable method of producing bamboo plants from callous tissue derived from seeds or immature plantlets, but the procedure has only recently been applied to bamboo in Australia. Micro-propagation techniques using emerging branchlets from mature culms might prove the most successful and cheapest method to establish a plantation, but this technique too needs more research.

CURRENT METHODS OF VEGETATIVE PROPAGATION

There are several methods of obtaining vegetative propagules. They depend on access to mature plants of the desired species from which various kinds of cuttings may be taken. These develop into new plants using the food reserves conserved in the parent material. Not all bamboos respond to these propagation methods. They seem to work best with thick-walled Bambusa and Dendrocalamus species and require high humidity and soil warmth for greatest success.

LAYERING WHOLE CULMS

Bend outer culms of a clump downwards after undercutting at the base and bury the culm in the soil after cutting off all but the main branches. After a few weeks, if soil temperatures are sufficiently high and moisture levels maintained, roots and shoots develop at the buried nodes. Saw off the culm sections bearing new plants and transplant these directly into the desired plantation area.

WHOLE CULM CUTTINGS

Whole 18 month old culms may be severed from adult clumps and planted in a shallow trench. Leave the top of the culm and a few branches intact and allow them to protrude above the ground. After some weeks, new roots and shoots develop at the nodes. Cut these from the parent culm and transplant them directly into the plantation site.

DOUBLE-NODE CUTTINGS

Make cuttings of culms with at least two internodes left intact. Trim branches from lower node. Plant prepared cuttings vertically in warm soil with the top of the culm and the branches left protruding. If using potting bags or pots, cover each with a clear or lightly frosted plastic bag tied in place after watering and leave in part shade until new roots protrude from drain holes. New roots and shoots are produced at the lower node. Single node cuttings planted on their side with the branch complement upwards will work with some species.

BRANCH CUTTINGS

Propagation using branch cuttings has proved successful in some cases. In Bangladesh, Melocanna bacciffera has been successfully propagated in this way. Cut the whole complement of side branches from a culm using a sharp hacksaw and plant in warm soil. Maintain atmospheric humidity using the system described for double node cuttings. New roots appear at the base of side branches within a few months.

Obtaining new plants using these methods can take up to one year. A few more years of growth are necessary before young plants are strong enough to produce new shoots suitable for cutting as vegetables.

GROVE MANAGEMENT

After about 7 years an equilibrium is reached where the number of new culms left each year equals the number harvested. For example, suppose there are 120 culms in a grove, and culms are harvested when they are six years old. There will be 20 culms of each age from one to six years old. In Spring, 20 of the new shoots are allowed to grow into new culms. In Autumn the 20 six year old culms are harvested and the garden is back to its original 120 culms.

A highly fertilised grove produces large culms with many branches and leaves. Because of the widely spaced culms wind damage to the rhizomes at the base of the culms is likely. To avoid this damage the culms should be topped. Topping also allows more sunshine to reach the ground promoting early shoot emergence.

The best time to top is just after the lowest 2 or 3 branching nodes have extended their branches and the upper branches are still enclosed in the sheaths. Count 12 nodes up from the lowest branches, and cut off the culm above it. Always cut the culm cleanly. Breaking it will cause ragged splits and provide entry points for disease.

 

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© The Australian Bamboo Network 2003