Tropical Water

Nelumbo nucifera, the sacred lotus, makes a spectacular display when flowering.

by Angela Hijjas

From The Malaysian Naturalist, vol. 52 no. 4.

Water and its lack or excess has become a much debated topic in KL, where floods alternate with droughts, and taps droop to a drip when rains miss the catchment and fall in the city heat sink instead. I am responsible for the supply of and demand for water over my 14 acres and have taken a deliberate role in retaining and modifying runoff so that it does not become a problem for others downstream.

My objective is to create a garden and landscape that is sustainable and can tolerate periodic dry periods or deluges. The basic pre-requisites for a tropical garden are plenty of both sunlight and water, combined to create the natural hot house. The strength of the sunlight is modified by shady trees that shape the landscape and give an important dimension of height as well as retaining humidity, but the appearance of water is the next most important element in fashioning a sense of landscape.

Two ponds, dredged along a natural stream and dammed at one end, contain a fair amount of flood surplus and retain enough in the dry season to maintain a lotus garden. In other areas of the garden, water is directed to long ‘soak aways’, sand and rubble drains buried in the ground that encourage water to soak into the ground rather than run off too quickly.

Salvinia, the floating fern that soaks up nutrients but can easily choke a water garden.

Not only am I trying to reduce runoff, but also to contain the loss of nutrients that can be dissolved and lost in just one heavy storm. An interesting lesson about the retention of nutrients came from my unwitting introduction of a floating fern, a variety of Salvinia, a pretty thing, thought I, that innocently came along with a water lily from a nursery.

I let it float off into the sunset, never imagining that it could propagate so rapidly that in a few months my pools were completely choked. Other plants that depend on sunlight were destined to die if we did nothing, so we started to scoop it out by the boat load and were surprised to find that the water underneath was crystal clear. The reduced sunlight had restricted algae and the plants had taken up much of the dissolved nutrients washed into the water from chicken dung fertilizer. Of course it grew back again, but it seems to be seasonal and at the moment is in remission.

The lesson learned was to make use of the scoopings for compost and mulch, thus harvesting the nutrients from the water rather than have it wash away. I would imagine water hyacinth would perform the same role. The collecting is labour intensive, but as in all gardening there is something very satisfying in making the most of what is available in the garden to improve it in some way, rather than merely buying a solution.

The main water feature is in front of the house where a raised reflective pond uses water from the dam to create a more formal pool. An architectural cascade draws water through a coral filter, installed ages ago more for fish rearing than planting. As the coral dissolves it makes the water too alkaline for plants. Water lilies and other plants will not thrive in alkaline water although it suits fish well enough. By contrast, the two natural pools had acidic water so now we mix the two. Submersible electric pumps draw water from the dam to the reflective pond, compensating for evaporative loss and balancing the pH of the water, maintaining more acidic than alkaline levels. The circulating and mixing also reduces the problems of stagnation, maximizing the effect of the reed beds around the dam to clean the water.

Water lilies, Nymphaea sp., come in many forms, that are either day or night flowerers.

We made planting beds in the reflective pool, using laterite for the planting medium as water plants prefer a high iron content. Planting holes were enriched with compost and muslin bags of chicken dung provide slow release nutrients beside each plant. The water depth for plants is about 30cm, but if you want to rear fish the water should be about a meter deep to ensure that the water does not get too hot from exposure to the sun. As the temperature increases the amount of oxygen available to fish is reduced, causing distress or death.

In keeping with my indigenous theme I have tried to limit myself to indigenous plants and fish, but with the inevitable invasion of tillapia that objective has been foregone. One of the most important lessons I learned, albeit too late, was never allow anyone, no matter how well meaning , to introduce this dreaded scourge into your pond; they breed prolifically from a young age and are near impossible to eradicate. The only way to control them is not to feed the fish and hope that a natural balance will be restored. Introducing a predator such as haruan or toman into the pool may help, and take heart in the assurance that some will be taken by kingfishers.

I restrict garden watering to a handheld hose, and then only in the vegetable garden and for the ferns around the house. Everything else has to survive on rainfall. Too much watering will encourage surface rooting amongst plants that would normally dig deeper and tap into more reliable ground water supplies. Mulching is critical to retain moisture, so don’t burn off leaves: either compost them or pile around a tree or shrubs that can do with the protection. Don’t, however, heap mulch close to tree bark as it encourages fungal attack; make sure there is breathing space around it. New plantings need water, of course, so try to plant in the wet season, or if in the dry dig your planting hole and fill it with water. Wait until it soaks away and then plant; at least the surrounding ground will not draw from the plant. And don’t forget to mulch; when it rots away do it again, and again! Not only will the soil develop a higher content of organic matter, it will retain moisture better and provide a perfect environment for micro organisms that work in soil to release nutrients for the plants.

Combined with the intense sunlight of Malaysia, an ill-conceived water garden can soon become an eyesore of algae and mosquitoes, with pumps clogged and filtration overwhelmed. I have been playing around with pumps and stuff for some time, and although my water garden is not yet the show piece I hope for, I am still learning. Playing with water is such fun, as my 3 year old grandson will attest, and to nurture damsel and dragon flies, lotuses and water lilies, and to see the flash of an occasional fish, must be the ultimate gardening reward.