As a generality, bamboos may be divided into two groups to accord with differing growth habits and natural origin. Tropical species are more likely to be of the “clumping” habit. That is, new growth springs up from close to the base of the mother plant to form, typically, isolated clumps of culms (as the upright stems are called) radiating from a center and growing outward in all directions to form a circular mass of vegetation. By contrast, temperate zone bamboos are characterized by the development of an open network of horizontal underground stems (rhizomes) from which the new culms grow. This invasive habit has earned this group the name of “running” bamboos. Intermediate or composite forms exist and habit may be modified by limitations imposed by the plant’s immediate environment.

Culms emerge from the soil and grow to full height within as little as two to three months. Exceptional growth rates have been recorded of as much as 1.2 metres in one day but the individual rate depends, of course, on the species and the growing conditions. The quantity of new culms, their height and diameter varies within a particular species depending on soil and air temperature, the availability of water and especially upon the age of the plant itself.                    

True equatorial environments encourage almost continual shoot production but where any seasonality is introduced the growth of fresh culms occurs immediately prior to the rainy season and continues until such time as conditions prove less favourable. Temperature, water and nutrient availability are critical determinants with regard to the number of shoots.                   

As a bamboo plant matures, the height and diameter of new culms increases each growing season until the optimum for that species and site is reached. However, as all bamboo culms lack the ring of growing material typical of tree trunks and their branches, there is no subsequent individual increase in girth from the late bud stage, only a pronounced, telescopic     elongation.   Perhaps the most noticeable characteristic of bamboo is the segmentation of the culm into distinct nodes or joints with intermediate smooth sectors or internodes. It is the elongation of these internodes that provides the basis for culm extension. As might be expected, tropical bamboos attain the largest size with culm lengths reported in excess of 35 metres and diameters to 30 centimetres.                   

Peripheral culm tissue is a dense matrix of elongated cellulose plant fibres cemented together by lignin to provide a strong and very flexible frame. Such a high degree of flexibility is essential in a plant that grows to a significant height yet is secured only by a shallow rooting system as is the case with bamboo.  Internal wall tissues are soft and serve as the path for the transference of water, nutrients and growth regulators through the length of the culm. 

The culms and their branches carry aloft the leaves to gain sunlight and to deny it to competitors: during the reproductive phase they bear the flowers and fruits: they hold the canopy beyond the reach of many would-be seed and leaf eaters and they serve in unison to trap and contain leaf litter as a future nutrient resource.

It is a common mistake to visualize each culm with its head of leaves as being an individual plant. They are in reality simply single shoots of a parent plant. The role of the culms has been elegantly described as being that of the fingers of a hidden hand. That hand, the true foundation of the bamboo, is the underground rhizome system. Just as the culm has many functions so too has the buried rhizome. As it is the only part of the plant in contact with the soluble salts of the soil it is, by virtue of the roots that spread from the nodal points, primarily a nutrient and water gathering organ. The rhizome also acts in a food storage capacity. Importantly, it is an anchor for the towering culms above and the nursery of future growth.

Bamboo root systems are seldom to be found penetrating any deeper than one metre and most of the underground growth is contained within 50 centimetres of the soil surface. Overall plant stability is obtained partly by the flexible structure of the culm, its particular method of attachment to the rhizome and also partly because the underground architecture, though shallow, is formed into a dense and firmly interwoven matrix. This applies to both the clumping and running types of bamboo. 

In the former, the rhizomes spread by the formation of lateral culm buds immediately adjacent to the base of an existing culm. Expansion is therefore both progressive and multidirectional following, typically, a circular pattern of colonization.

The runner type of bamboo has a quite different root mass structure consisting of fast growing and far ranging rhizomes bearing buds that may variously develop into culms or secondary runners. Their seasonal rate of growth depends upon the totality of the physical and chemical soil characteristics and is typically between two and five metres although this growth may not be unidirectional. The effect of this root elongation habit is to enable the plant to quickly invade surrounding areas and so to gratuitously locate and exploit any favourable localised resource. The repeated lateral branching of the rhizomes creates a strong and highly interwoven network of fibrous growth that supports the plant, stabilizes the soil and discourages competition.

All bamboo rhizomes are configured in the same nodal format as are the culms, the internodes typically hollow in runners and always solid in those of the clumping species. 

At each node of the underground rhizome and of the aerial culms and their branches, protective sheaths cover the sensitive growing cells. In most cases this sheath falls off as tissues mature but in some instances is retained as an on-going protection.

Branches arise from the nodal points of culms. The number of such branches, of associated dormant buds (if any) and the height along the culm at which branches do or do not emerge depends upon the habitat niche to which the particular species is adapted. Bamboos that naturally form a dense and dominant canopy maintain uncluttered culms up to the level that sunlight can effectively and efficiently be employed in photosynthesis. Understorey species or those growing in more open environments produce branches along a greater length of the culm. Several bamboos bear modified branches in the form of thorns which commend them as hedging plants. 

Branches are primarily the leaf bearers. Bamboo is an evergreen plant whose many leaves are continually being replaced and so tends towards the accumulation of a substantial and, for competing plants, stifling ground litter. Leaf fall is perhaps greater in the early spring when kinder growing conditions enables young growth to replace those leaves that have survived the winter. As with everything else bamboo, there are wide variations in the size of leaves between species although their general arrangement is sufficiently familiar as to be easily recognizable. Unlike other grasses, bamboo leaves have a stalk and are therefore not a simple continuation of the branch stem sheath although they arise from it.

One of the most vexing yet fascinating aspects of bamboo study is the issue of bamboo reproduction. Bamboos are flowering plants. Their mode of flowering, the structures of the flowers and the fruits are not dissimilar to those of other grasses.  With one significant difference.  Bamboos mostly flower sporadically and may do so in a periodic pattern that can span anywhere between twelve months to over a hundred and fifty years. As if by some built-in clock, a species of bamboo after years of vegetative growth begins to bloom, not just in the one grove but across districts, countries and whole regions.  Then, either exhausted by or satisfied with this momentous effort, the plants in unison wither and die. Entire forests are destroyed. Juvenile cuttings, recent growth and ancient stands alike are reported to all join in this flowering and dying phenomena. It is called gregarious flowering and is the most discussed and perhaps least understood issue in bamboo science.  

Inevitably, such a dramatic natural occurrence affecting so many important aspects of Asian daily life is indelibly woven into the common folk lore but the true periodicity, the extent of the flowering, the degree of loss to established groves and the boundaries of the areas affected are seldom as well defined or complete as is perhaps reported. However, gregarious flowering certainly does occur and the mechanism controlling it remains as yet unidentified. The commercial implications of this wholesale population decline are substantial.

Between these periods of flowering and sexual reproduction, bamboos actively propagate themselves by vegetative means. Clumping varieties, by establishing new culm growth at the perimeter of their particular stand, progressively encroach upon and suppress other plants that are competing for resources in the immediate vicinity. However, if the stand is damaged or broken up, the nodal buds on the separated culms have a very high chance of forming new plants although the original fragmented rhizomes are less likely to survive and regenerate.

The opposite is true for runner bamboos.  In these it is the remote underground rhizome that gives rise to new culm growth and the invasive habit of this root system ensures a rapid occupation of territory either by-passing or overcoming other plant communities as opportunity provides. If damaged and the area substantially disturbed, it is the rhizomes that survive and generate clonal regrowth.   Even in the nursery the culms of runner bamboos resist vegetative propagation and are not likely to substantially contribute to re-establishment in the natural environment.

If the point has not been sufficiently laboured it is necessary to reiterate that bamboos, although sharing many common features, are not by any means all alike and that even within a particular and identified separate species considerable variances may present themselves.

Much of this variation may be a reflection of the effect of long intervals between sexual reproductive generation. Cross fertilization, as an essential part of the sexual reproduction process, introduces homogeneity into a population. Protracted periods of clonal propagation without the averaging effect of cross breeding invites the survival of genetic diversity. Other apparent anomalies within a species may be the result of incorrect classification by botanists unable to check their results by reference to flowering material.                       

It is primarily by the particular design of the inflorescence that the flowering plants are traditionally and most reliably identified. In the absence of suitable data, bamboo species have been cautiously and variously described on the basis of growth habit, the frequency and arrangement of branches, buds, protective sheath details, culm size and colour, leaf size and arrangement as well as the presence or otherwise of hairs, thorns and other commonly occurring features. The degree of uncertainty regarding bamboo classification may be judged by the tentative estimates given in the scientific botanical media that there may be between thirty to ninety genera and in the order of five hundred to fifteen hundred discrete species!  Varietal diversification by adaptation to discrete, local habitats is very much in evidence.                

The rapid generation of biomass of which all bamboos are capable suggests that it is a rich or at least a very efficient feeder. Soil conditions vary substantially over the large geographical range that bamboo occupies but since most tropical forest soils are high in humus, are friable, moisture retentive and slightly to mildly acidic then such a soil condition is likely to represent the reasonable average for bamboo generally.  Some bamboos are drought resistant but typically they exhibit far better growth and condition where water is plentiful and the soil well drained. Salt tolerance is not a feature so far identified in any bamboo.

Durnford Dart – September 1994

At least 40% of the forest cover in Mau has been depleted by deforestation and encroachment.  In the Aberdare Mountains squatters wanting to farm, illegal loggers, hunters, villages wanting firewood and corporates trying to source illegal water for flower and vegetable farms is harming the bio-diversity.

Prior to the ban on exploitation of indigenous trees in the mid 1980s, Bamboo stems were exploited for domestic uses mainly for fencing and construction. Due to its high rate of regeneration the controlled exploitation of bamboo has no negative impact on catchment value of the forest.

The Bamboo Trading Company approached Durnford Dart to determine the feasibility of growing and harvesting bamboo in a sustainable manner in these areas. They planned to rehabilitate one forest concession on the Mau and another on the Aberdare.  However there were no management plans for bamboo forest and the ban of exploitation of indigenous tree species would affect harvesting of bamboo.

The forest concessions would produce a valuable source of wood biomass for the nation and at the same time restore wildlife habitat, control erosion and preserve water quality in catchment areas.

In 2012 Durnford was engaged to establish the biomass productivity of the bamboo in different zones of the Aberdares and Mau and then to establish the most cost effective method of management, propagation, reforestation and harvesting. Commencing with a field work feasibility study in 2012, he recommended propagation methods, grid measurements for planting, provided information on care, maintenance and harvesting and the necessity of stockpiles to prevent harvesting during new shoot emergence.

Durnford concluded “I am impressed with the many qualities of Arundinaria alpina, it’s biomass productivity is good, it’s ability to cloak the hillsides in a natural monoculture supporting biodiversity is good and it’s shape and size make it easy to use commercially.”

Aerial views of the Aberdares (left) and the Mau (right) showing where areas of bamboo have been replaced by agriculture – in this case tea

In 2015 Arris won the tender to install a new wastewater treatment and dispersal system at the Keppel Sands Caravan Park, owned by the Livingstone Shire Council.  The site is situated close to sensitive areas such as creeks, waterways, coastal dunes and human habitation. A Rhizopod was designed with a fully contained recirculating hyrdroponic pod system utilising plants to beneficially use and disperse the wastewater. Durnford Dart was consulted to select  the best bamboo species for the project and provide the root stock.

With water usage fluctuating depending on the season, a plant that could resist environmental stresses, like too little or too much water, was required.  According to research funded by the European Commission, bamboo is effective in phytoremediating water. Phytoremediation processes use natural materials to eat up pollutants, making them distinct from processes that capture contaminants and dispose of them elsewhere.  Bamboo has a high water and nutrient usage and saw the effluent as liquid fertiliser, producing a fantastic growth rate.  As water passes through the plants, the bamboo roots act as a filter, drawing out toxins and impurities, thereby cleaning the water.

Using bamboo allows wastewater to be evaporated or transpired without leaching into the environment or contaminating overland flows.

The essence of all sewage and effluent treatments is to physically separate dissolved, suspended and floating inclusions from the water base. Sludge tanks, screens and centrifuges can remove much of the solid waste. Induced chemical reactions may serve to precipitate further foreign matter and so render it accessible to screening. Ultimately, the strained liquid is exposed to biological agents for the safe conversion of the dissolved pollutants into filterable inert residues.

The results of successful biological interaction generally lead to either additional recoverable solid wastes or to gaseous compounds easily dissipated by agitation and ventilation. Inevitably, most water treatment managers seek to release treated effluent from their care at the earliest stage that opportunity, regulation, funding or conscience allows.

Biological exposure may vary from the crude spraying of diluted human and animal sewage directly onto pasture through to very complex, multiple stage processing plants. The direct spraying of nominally treated wastes is an ancient and quite acceptable agricultural practice providing necessary care and understanding are applied to ensure that the water-borne pollutants are indeed capable of being fully broken down before the residual water is taken back once again back into the natural drainage and groundwater systems. It is very much a question of establishing a balance between concentration and dissipation.   

Land, for example, that is sprayed with piggery effluent will very soon become “pig-sick” if the rate of natural biological breakdown in the soil is overtaken by the rate of effluent deposition. Pasture growth falls off, the risk of animal disease escalates alarmingly and neighbourliness plummets. Rainfall, temperature and the phase of seasonal growth obviously have a variable and controlling influence. There is also the danger that certain elements, harmless in low concentrations, may over time accumulate to toxic proportions and be subsequently incorporated into some form of harvested crop or inadvertently released back into the water supplies.                  

Certain prerequisites must therefore be satisfied before irrigation with partially treated effluents should be contemplated.

1. The area over which spraying is to take place must heavily err on the generous side if natural precipitation and flooding are not to be allowed to interrupt spraying.
2. Land utilisation must not be such that effluent residues can find themselves either directly or indirectly in the human food chain.
3. The vegetation and soil, in combination, must have the capacity to arrest, absorb and convert all the non-water components as well as controlling the rate and impact of water transfer.

The first parameter to be considered is that of site: size in relation to the volume of effluent to be treated, proximity to the effluent source, limitations imposed by planned or existing utilisation, the nature of the soil and the characteristics of the water table. If some produce is to be gleaned from the irrigated land then suitable access for maintenance and harvesting and a workable proximity to markets are necessary further considerations.  

The system design must first address those basic water management issues raised by any normal irrigation project. The means and cost of delivery, of dispersion, drainage and maintenance.                 

Finally, the determination of the nature of the intended vegetation – natural or farmed – is critical to the success of the venture.                

Contemporary society recognizes the need to safely convert industrial as well as sewerage wastes. Experiments have been conducted in Australia to accommodate the effluent from mechanical process pulp mills by spraying it into pine plantations destined to become feedstock for the same mill. This is an elegant solution. The improved growth of the trees brought about by  irrigation naturally boosts the productivity of the plantation whilst at the same time accommodating both effluent disposal and the provision of a locally valuable product that is independent of the food chain. Trial plots have been studied, judged successful and expanded. 

Well, if it all works so well why bother to introduce bamboo at all?  Simply, it can be made to work even better still. There are of course as many different applications as there are problem effluents. But consider the pulp mill situation referred to above.

1. Pine trees may take up to fifteen years or more before they are ready to harvest. That is a lot of pumped irrigation and a very long investment time in capital plant and maintenance before a tangible return can be realised. Bamboo may be cropped after only three years and may then be regularly, annually harvested without having to destroy the original plantation or the soil covering as is normally the case with softwood felling.
2. Compared with softwood trees, bamboo’s faster accumulation of biomass combined with the advantage of an annual cropping cycle commencing only three years after initial planting means that much smaller areas of plantation are required to satisfy both the need for effluent disposal and feedstock production. Capital and maintenance costs are correspondingly reduced.         
3. Demand for paper products, although showing a progressive upward trend, does fluctuate over time especially with regard to particular products and the impact of unforeseen competition. Tree plantations, locked into a minimum of fifteen but sometimes a thirty year cycle, create a vulnerable inflexibility for the industry. The versatility introduced by a three year cycle means that bamboos of different characteristics can be established to fill new requirements or existing plantations manageably expanded to satisfy an expanding market.
4. With so many fast growing, large, tropical bamboo species acclimatised here their enhanced production, say, in comparison with the slower growing pines in cooler regional climates means that the cost of pulp may be maintained at not only a viable but, indeed, at an internationally competitive level.

 Bamboo as a source of paper pulp has no history in Australia. Both India and China use bamboo extensively although, in deference to the ready availability of process know-how and machinery from the West, both might well perhaps prefer to have easy and economical access to softwood trees. But they have no such access so must apply themselves to a prolific resource that is much more readily obtained. In this they mirror the endeavours of our own early paper manufacturing industry which only reluctantly turned to softwood feedstock a little more than a century ago and, far more recently still, learned to employ eucalypts for pulping.                 

Prior to the Second World War, eucalypts were quite unsuitable for pulping according to the papermaking establishment. A little adversity, a shortage here, a price increase there and guess what? Yes, a breakthrough – “eucalypt” is the wonder tree exported around the world! So it will be with bamboo: too hard today because we have a naturally growing alternative, indispensable tomorrow when that forest resource becomes increasingly difficult to harvest and pine plantations fail to meet the financial returns obtained by cultivated bamboo.                 

Overseas experience indicates that mixed stands of trees and bamboos can provide benefits to the growth performance of both. Certainly this is something that should be tried here especially within a waste water treatment project. Reports show that the interaction of different plant storeys and the more complete ground cover has substantial and beneficial effect upon ground temperature, frost incidence, humidity as well as an increase of biomass and ground litter. The shallow rooting habit of bamboo complements deeper tree root systems to uplift the maximum amount of nutrients from the soil. Such dual planting also suppresses weed proliferation, accelerating the growth of each component. The diameter, height and straightness of both timbers have been shown to be substantially enhanced whilst the inhibition of side branching provides a natural and beneficial pruning.

Not all pollution problems are associated with toxic outpourings from residential and industrial complexes. The serious and continuing hazard of blue-green algae in our waterways highlights the need for an effective, passive but continuing deterrent to that concentration of soil nutrients which has been identified as encouraging algae growth.  In this application irrigation water may not be either freely available or economically feasible to provide. Hardy and vigorous plants that can proliferate in a range of conditions, and by so doing take up and retain within their biomass the nitrates and phosphates already in the soil, must therefore be provided. If, in addition a worthwhile crop can be harvested from such plants  then all the better for, by this self-financing means, incorporated nutrients are progressively removed from the area. Of course, bamboo!

The Chinese forester makes automatic recourse to bamboo when putting in place soil erosion and water catchment protection schemes. An assurance based on generations of experience allows, without further debate, the planting of thousands of acres in hundreds of projects along vital waterways throughout China. In Australia, ignorance all too often gives rise to rejection. Quite apart from the arrogance implied by our disbelief of generations of human practical, tangible and visible accomplishment, the reluctance of local authorities in Australia to trial bamboo as a protective soil cover even in the most demanding and urgent of situations signifies a general lack of both intellectual curiosity and self confidence that bodes ill for this nation’s future.

At the forefront of this insular thinking is, surprisingly enough, the formally trained farming and environment professional. Of course, we are all of us familiar with the errant bamboo in the backyard but we are not talking backyards here but critical waterways whose banks are scored by erosion and streams poisoned by excess nutrient wash. Also, and quite understandably, no scientist is keen to gain the same kind of fame as attaches to the original promoters of the cane toad. However, responsible caution is one thing, narrow parochial refusal to acknowledge well researched and proven practices quite another.

The qualities of bamboo that incite opposition are its rapid growth and dense root matrix, yet these are exactly those characteristics that are essential for effective soil protection and conditioning. A rapid accumulation of biomass, evergreen canopy, ample ground litter, vigourous surface root extension and general hardiness are mandatory whether it is bamboo or some hitherto undiscovered Australian native that is to be employed. It is to the advantage of bamboo that it does not spread by uncontrollable seed dispersal, it cannot invade or block. water channels and is not poisonous to either native or domestic animals. Moreover, mature stands can be successfully and regularly cropped for economically valuable timber and for edible vegetable shoots without the slightest interruption of the soil binding role. No Australian native can meet this demanding specification.             

Research in India has demonstrated that for one common species of bamboo the potential for nitrogen uptake was such that, when made freely available, culm yield increased by 15 times – not 15 percent but multiplied by fifteen! The research confirmed that nitrogen had the greatest influence on growth and biomass production closely followed by potassium. Phosphorus showed a marked influence only in conjunction with nitrogen. As is to be expected from the variety of habitats naturally occupied by bamboo, different species have quite distinct appetites when it comes to nutrient uptake. There is the potential therefore for a close matching of plant and circumstance when setting out to arrest excess nutrient contamination.                 

In Yunnan and Fujian provinces of south east China, capital intensive, professionally engineered river bank protection schemes proved less successful during a period of extreme weather conditions than did adjacent natural bamboo groves prompting authorities there to speed up and extend their re-afforestation programs in water catchment and river systems.   Similar experience in Japan has shown that even heavy flooding and the damage caused by floating debris will not deter the rapid regrowth of bamboo. Indeed, flood damaged areas responded with an above average growth in the following two seasons.

Contrary to superficial opinion, bamboo need not expand indefinitely to become in turn a menace but can be contained providing the species and situation are properly matched at the outset. What we badly need in Australia is a Shire Council with the resolve to address the problem (backed by the relevant research and academic institutions suitably purged of parochial botanists) to trial bamboo plantations on a workable scale so as to reproduce here the findings of overseas communities.  The rewards for such an endeavour may well extend beyond the necessary but isolated objective of nutrient uptake. Bamboos planted for this purpose can also provide income and employment to rural communities by the sale of harvested products as well as from such secondary manufacturing activities that bamboo plantations of sufficient scale universally generate. Just as importantly, bamboo will curb soil erosion and, if so desired, provide in time an effective natural barrier to prevent the passage of cattle and further damage to the banks of waterways.

Durnford Dart – September 1994