Water spinach

Note Number: AG0897
Published: March 2002
Updated: June 2012 and September 2013

Amaranth species follow the C₄ pathway in photosynthesis (over 95% of plant species have C3 pathways). This pathway occurs only in a few other crop plants such as maize, sorghum and sugarcane, and enables the plant to use light and water more efficiently in converting CO₂ to carbohydrate. This is particularly advantageous when sunlight is abundant.

Introduction

Chinese spinach (Amaranthus gangeticus) belongs to the Amaranthaceae family, and is one of a number of cultivated species. The Amaranth family is a very large group of plants, which also includes a number of important herbs of the tropics. The Amaranthaceae family has originated in the topics of America, Africa and Asia, but the plants belong to this family are now grown all over the world.

The average height of mature Chinese spinach plants is about 35 cm, but some species can grow up to 150 cm tall when flowering occur.

The leaves are soft-textured, and go limp quickly after being picked. They can be pointed or round, and vary in colour from light to dark green, with a reddish centre or red markings.

The leaf variegations range from dark green, brown, and red to golden yellow. Leaves also vary in size, the largest being fairly broad and up to about 15 cm long. In some varieties, the leaves are much smaller. Large-leafed forms seem to be more vigorous than those with small leaves. Stems are soft and juicy, and are very often blotched with red.

The numerous small seeds produced by Chinese spinach are edible. The flowers are small, crimson or greenish in colour, and are borne on erect terminal clusters, which grow up to 20 cm long, appear in late summer and are not edible.

The leaves are nutritious; rich in protein, magnesium, iron, calcium and vitamins A and C. Chinese spinach tastes somewhat like artichoke, but can develop a 'hot' taste in older plants.

Chinese Spinach has different names according to language and dialect, with some examples being Amaranthus, Edible amaranth, Edible amaranth spinach, Bayam (Malaysia and Indonesia), Calaloo (Caribbean) and Klaroen (Surinam). It is also named Xian cai in Mandarin, Yin choi/In tsoi in Cantonese and Hi-yu-na in Japanese.

Uses

Very young leaves and stems are used raw in salads. Colourful red leaves look most attractive. In cooked dishes, Chinese spinach is used very much like spinach and can be substituted in any spinach recipes. It cooks faster than normal spinach, so more care should be taken not to overcook it. It is best treated simply: steamed, stir-fried, and mixed in with meat or fish dishes.

In Asia and the West Indies, Chinese spinach is widely used in soup. In Jamaica, it is routinely eaten at breakfast and dinner.

Growing requirements

Climate

Chinese spinach can be grown in both tropical and temperate zones. Humid, sunny conditions are advantageous but not essential for growth. However it will not tolerate frost or freezing temperatures. Some varieties grown under cover or outdoors in a warm climate are liable to self-seed, and can easily become weeds.

Soil

Although the crop can be grown on a wide range of soils, Chinese spinach performs best in light, sandy and fertile soil.

Good soil drainage helps to alleviate problems with root diseases, and can be achieved by using raised beds. Amaranth tolerates fairly acid soils, with a pH range between 5.5 and 7.0. If soil pH is lower than 5.5, a dressing of agricultural lime or dolomitic limestone should be applied at least a month before sowing and earlier if the soil lacks adequate moisture.

Crop management

Sowing

The soil temperature should be above 10°C to achieve good germination. In heated greenhouses, first sowings can occur very early in spring. After all risk of frost is over, seeds can be sown outdoors.

The seeds are sown directly into beds, and successive sowings every fortnight are used to give a longer cropping period. The seeds are very small and should be sown after first mixing with coarse wet sand.

Chinese spinach germinates best in the dark, so cover seed well after sowing. Sow the seed 15 mm to 25 mm deep in rows. Seedlings appear 2-3 weeks after seeds are sown, and can be transplanted out when about 2 cm high and showing 2-3 true leaves. Thinning is usually necessary after direct seeding, and can be done 2-3 weeks after sowing, when plants are at the two to four leaf stage. Final plant spacing should be 8 x 8 cm. The larger of the thinned plants can be used for eating.

Chinese spinach can also be propagated from cuttings, which are usually taken from younger growth or side shoots that have not flowered.

As the crop grows best in light and loose soils, regular hoeing is advisable to prevent the soil from becoming compacted.

Nutrition and irrigation

To produce quality Chinese spinach, the crop must be given sufficient nutrients. Weekly applications of fertiliser to provide 18 kg/ha N, 18 kg/ha P and 36 kg/ha K, is recommended for high yields.

Farmers who use chemical fertilizers should be aware of the potential dangers of using phosphatic fertilisers with high levels of cadmium.  Research has shown that the use of phosphatic fertilisers which contain the heavy metal cadmium as a contaminant can increase cadmium levels in both soil and the produce. There are legal maximum levels of cadmium allowable for vegetables sold in Australia. Fertilisers containing cadmium in excess of 1 mg/kg are required to state the following warning:

"WARNING - this product contains cadmium.  Continued use of this product in agricultural situations may lead to residue levels in plant and animal products in excess of the maximum level specified by the Australia New Zealand Food Standards Code and the accumulation of cadmium in soils."

It is in the grower's and consumer's interests to minimise the addition of cadmium to soils and agricultural produce.  Growers should consult fertiliser suppliers or manufacturers for advice on the cadmium levels of fertilisers they are considering using.  There are a number of low cadmium horticultural fertilisers marketed today.  These have lower levels of cadmium than some superphosphate and other fertilisers.

Fowl manure is a good source of organic matter and nutrients. If deep-litter fowl manure is applied at a rate of 200 bags (22 cubic metres) to the hectare, then the fertiliser rates can be reduced by one third. Fowl manure must be worked into moist soil more than six weeks before sowing, as mites from fowl manure and crop residues can damage the crop.

Chinese spinach should be irrigated to keep the soil constantly moist for succulent growth, but the crop cannot tolerate wet soil.

Pests and diseases

Many chewing insects such as vegetable weevils, mites, caterpillars, cutworms and grubs attack Chinese spinach.

It is recommended that seed not be sown into a recently cultivated area where an old crop has been worked into the soil.

The fungus, Choanephora spp, causes wet rot of leaves and young stems, and Pythium spp causes damping-off of seedlings. Fusarium spp. also affects the crop and the disease can be managed by practicing long rotations and using "new" ground for summer crops.

Chinese spinach is also susceptible to nematodes and bacterial wilt.

Harvesting and storage

Chinese spinach takes 6-8 weeks from sowing to reach the cropping stage. There are several ways to harvest the crop.

Tips of larger plants can be picked while quite young. Alternatively the whole plant may be pulled from the ground, roots and all, when approximately 25 cm tall. Chinese spinach can regrow rapidly so an alternative method is to cut mature plants back to 3 cm above ground level, leaving some of the stem and a few basal leaves to promote regrowth.

Growth depends on temperature, but by using these methods, harvesting can continue over several months for the smaller-leaved varieties. Any flowers, which appear, must be removed.

In the tropics, up to 10 harvests are possible from the same area each year. Total yield may rise to 40-80 t/ha if the crop is harvested by repeated cuttings or thinning.

Because Chinese spinach can be sold as whole plants, it keeps better than most other leafy vegetables. The plants can be wrapped in a damp towel, encased in a plastic bag, and refrigerated for up to a week before use.

Marketing

There are certain times of the year when Chinese spinach is in demand such as during the various ethnic holiday celebrations; particularly in the Indian and Indonesian communities. In early spring, leaves are young and tender, so they can be generally sold loose, not bunched. Some green grocers sell Chinese spinach as bunches. Crushed ice may also be used in containers of Chinese spinach sent to distant markets.

Further references

Dahlen, M (1992) A Cook's Guide to Chinese Vegetables, the Guide Book Company Ltd, Hong Kong

Fenton-Smith, J (1995) A Grower's Guide to Vegetables, Murdoch Books, Sydney, Australia

Graham, J (1984) Cooking with Herbs and Spices, Reed Books Pty. Ltd. NSW, Australia

Hackett, C. and Carolina, J (1982) Edible Horticultural Crops, Academic Press Australia

Hillhouse, C (1991) Vegetable Amaranth, Vegetable leaflet, The Small Farm Centre, University of California, USA

Larckom, J (1991) Oriental Vegetables: The Complete Guide for the Gardening Cook, John Murray Ltd. London

Nguyen, V. Q (1992) Growing Asian Vegetables, Affect H8.1.37, NSW Agriculture.

Contact/Services available

Correct diagnosis is essential for effective pest and disease control. A commercial diagnostic service is available at the AgriBio Bundoora.

For further information, phone Crop Health Services on (03) 9032 7515.

For further information on registered chemicals, phone our Customer Services Centre on 136 186.

Acknowledgements

This Agriculture Note was developed by the Farm Diversification Information Service of Bendigo, Murat Top and Bill Ashcroft, DEPI in March 2002.

It was reviewed by Farm Services Victoria in June 2012 and September 2013.

ISSN 1329-8062

Published and Authorised by:
Department of Environment and Primary Industries
1 Spring Street
Melbourne, Victoria

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