A GROWER'S GUIDE TO CULTIVATING CHINESE WATERCHESTNUTS IN AUSTRALIA
This booklet is the result of more than three years of research funded by RIRDC, and jointly conducted by Central Queensland University and Eco-lodge-ic. It summarises research findings and experiences of growers of Chinese waterchestnut in many parts of Australia in an easily readable style. All aspects of production ranging from planting material and cultivation techniques, to postharvest, marketing and farm economy are covered. The guide is illustrated with many colour pictures.
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THE PLANT - Water Chestnuts ELEOCHARIS dulcis is a sedge that grows on water margins and bogs. It is an annual that has erect, narrow, tubular leaves (correctly known as culms) half a metre to a metre tall. The plant spreads by creeping rhizomes which produce additional sucker plants through the summer months. One chestnut (corm) can, under favourable conditions spread and fill a square metre. Later in autumn the leaves start to yellow and the chestnuts form at the terminal ends of the rhizomes. Over the following weeks the leaves die back totally and harvesting can start at this time. Although we find that the sweetness of the chestnuts improves after a period of winter chill. We begin our harvest on the 1st of July which is a month or so after the tops have died off here.
ORIGIN - ELEOCHARIS dulcis grows in many parts of India, SE Asia, New Guinea, Northern Australia and Polynesia. Some varieties are not sweet and are grown for starch and pig food etc. The native Australian variety is small but quite sweet and it is one of the main foods of the six and a half million Magpie Geese in the Northern Territory. Logs of the explorer Leichhardt not that "it was the tastiest native food offered to him by the Aboriginals". The variety we supply comes from China where it is know as Hon Mati, it is superior in size and sweetness.
SEED CORMS - The size of corms we harvest are variable and typically 80% of our crop is large enough to supply to the market as food. The remaining 20% are retained for replanting or supplied as seed corms. As with seed potatoes they are genetically identical to large ones and so, will not led to small corm size in future crops. The largest size they can be expected to grow to is 50mm in diameter.
SOIL - Water Chestnuts grow best in a rich, friable soil well manured or fertilised. We get excellent results from our padi which is constructed on a section of creek flat with a fine loam top soil and clay base. We fertilize with moderate amount of poultry manure. Our water source is from a dam with a high nutrient level. Experiments in the USA indicate that the major nutrient uptake by a crop that yielded 4700kg/h were nitrogen 108kg/h, magnesium 37.5kg/h, and calcium 6.9kg/h. The uptake of phosphorus and potassium was relatively low. The ideal pH range is between 6 to 7.5 so use Dolomite (a form of lime that contains magnesium) to adjust pH where necessary. Since Water Chestnuts are best harvested by hand which minimises damage to the fragile skin, it is important to have soil that is as free of hard debris as possible (stones, woody materials etc.).
WATER - The soil should be kept flooded with 100mm to 300mm of water throughout the growing period. A greater depth of water is tolerated by the plants but they do not prosper Water is drained off prior to harvesting. When filling containers with soil be sure to allow for 100mm of water.
SITUATIONS & CONTAINERS - They can be grown in any medium to large container that holds water eg. Old bathtubs, kids wading pools or Styrofoam broccoli boxes. Alternatively, you can grow them in a plastic lined trench in the vegetable garden. On a larger scale they are grown in flooded fields like rice. These fields are ideally located below a water source like a dam so that the water level can be maintained with a gravity flow. They can also be grown on dam and pond edges but only if the water level is controllable and stable.
PESTS & DISEASE - The only serious problems that commonly occur, that we are aware of, is rot and damage from birds. A total or almost total lost of seed corms due to rot can occur if they are introduced to a soil or medium that has been freshly fertilized with manure. This can be avoided by fertilising the field or container a few weeks early giving the manure time to break down first. It is often a good idea to start the chestnuts growing in a lower nutrient nursery plot in the mean time and transplanting later when the plants are about 300mm tall. Start by transplanting 1 or 2 plants watch their progress for a week or so. If they are still green and looking healthy transplant the rest. We find a small amount of rotten corms when harvesting but we dont consider that a problem. Grass Hoppers here also do minor damage.
The most serious problem that we have encountered is damage and pilfering by Eastern Swamp Hens. These native birds pull out young plants to get at the corm which is often still attached. During the growing period the birds continue pulling up and trampling leaves and building there platform nests out of them. Since resorting to protecting the crop with bird netting or yields have tripled and average corm size is substantially bigger.
STORAGE - Harvested corms can be stored in the bottom of the fridge in sealed plastic bags or containers to prevent them from drying out. There are always a few that rot during storage and need to be sorted out from time to time. This rot is often due to even slight damage to the skin during harvesting & later handling. They keep quite well in the ground where they grew while the temperature stays low enough to maintain dormancy. Dried out corms or ones that have been frozen will not grow. They also keep very well in cool damp sand. We have kept corms like this for well over a year in perfect condition.
EATING WATER CHESTNUTS - They are as much appreciated for their crisp texture as for their delicate sweet flavour. After cooking they retain their crisp texture even after leftovers are re-heated. They should be thoroughly washed then peeled by first cutting of the top and bottom and then peeling the remaining skin. They can be eaten raw or added raw and sliced to salads and clear soups. In Asia they are made into a drink by either blending raw chestnuts in water or boiling them or their skins in water for 15 to 30mins and adding a little extra palm sugar to enhance the flavour. The drink tastes like water that has have sweet corn boiled in it and it is reputed to have cooling properties, popular on hot days in Asian cities.
Cooking, and it need only be brief, either by boiling or frying improves the flavour and texture. They can be added to stew, soup, curry, stir fries and almost anything. They are a common ingredient in many Asian dishes; check your cook books! Be assured also that the fresh product is far superior to canned ones!
Disclaimer - The information here is given in good faith drawn from our own experience and because people apply advice differently and under varying conditions we cannot guarantee success.
Water Chestnut Starter Pack - 10 corms plus growing instructions for $30 post paid. Bulk corms - $60 per kilo post paid. Available from July to December.
Please send comments or enquiries to Hans Erken
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