Scientific name of New Zealand spinach is Tetragonia tetragonioides and it belongs to the family Aizoaceae. Scientific synonyms are T. expansa and Demidovia tetragonioides. Tetragonia tetragonioides or New Zealand spinach is a dicot plant grown for its edible leaves. The plant has a dense, spreading growth habit with its trailing stems have a tendency to form ground cover if its growth is unchecked. However, for vegetable purposes, it is grown and trained as an herbaceous annual bushy plant. It is perennial in its natural growth habit.
Common names of New Zealand spinach are Warrigal cabbage, ice plant, ever bearing spinach, everlasting spinach, perpetual spinach, Warrigal greens, sea spinach, Botany Bay spinach, tetragon, tetragonia, and Cook’s cabbage.
Botanical Description: It is a low growing, vigorous, spreading and much-branched herbaceous plant that reaches up to 30-40 cm in height upon maturity with a spread of about one meter. Its stems are trailing and mat-forming. Leaves are 3–15 cm long, thick, succulent, and triangular-shaped. Leaves are bright green in colour with a lettuce-like flavour. The plant flowers during spring-fall season. Inflorescences and flowers are yellowish in colour and are borne on 2 mm long peduncles. Fruit is a small, hard pod of 8-12 mm length which is covered with 4-6 small horns. Seeds are smooth and irregularly-shaped.
Origin and Distribution: New Zealand spinach is believed to be a native of coastal areas of Australia, Tasmania, New Zealand, China, Taiwan, southern South America, and some Pacific Islands, including Japan.
Food Uses: New Zealand spinach is used and cooked like other spinach herbs. It is used in salad greens, soups and vegetable dishes. New Zealand can be preserved by freezing just like spinach. Raw leaves are not suitable for consumption because of the presence of oxalates in them which may be allergic to some people. Blanching of leaves is done to remove oxalates just before cooking the leaves. Blanching is a process where freshly harvested leaves are immersed in hot water for a minute and then these leaves are rinsed with cold water. New Zealand spinach is cooked as a major vegetable dish or may be pickled. Blanched leaves may be used as an ingredient in salads. It may also be used in soups and stews, and as an ingredient in pastas and omelettes.
Nutrition in New Zealand Spinach: It is low in calories, proteins, carbohydrates and fat, but high in minerals and vitamins. According to USDA, 100 grams of raw, New Zealand Spinach gives about 14 kcal of energy. It also contains 94g water, 1.5g protein, 0.2g fat, 2.5g carbohydrates, 1.5g dietary fiber and 0.29g sugars. It is an excellent source of vitamin A, with 4,400 international units (IU) per 100 gram. Other notable vitamins include 30 mg of vitamin C per 100 gram of edible portion. It is rich in minerals such as 130 milligrams each of sodium and potassium in 100 grams of edible portion and 58 milligrams of calcium, 39 milligrams of magnesium and 28 milligrams of phosphorous in 100 grams of edible portion.
Growing Practices for New Zealand Spinach: The crop is best grown at an altitude of 1000-1700 meters from mean sea level. It is drought tolerant but does not like scorching heat. The plant prefers a moist environment for its growth. Flavour of leaves is well-developed when the plant is grown with consistent moisture.
New Zealand spinach prefers full sunlight for its healthy growth. New Zealand spinach may be grown in a wide variety of soils. However, the most ideal soil for its healthy growth is well-drained, fertile, sandy soils, which are rich in organic matter (humus). Ideal soil pH is 6.8 to 7.0. The plant grows well in saline conditions. Propagation is by seeds.
In warmer tropics, sowing is done 2 to 3 weeks after last frost. In colder areas, seedlings are raised indoors 2 to 3 weeks before last frost and later transplanted in the site 2 to 3 weeks after last frost. Before planting, the seeds should be soaked for 12-24 hours in cold water, or 3-5 hours in warm water. This will facilitate easy germination. It may take 10-20 days for seedlings to emerge.
Direct seeding in groups of 3 seeds is practiced if it is grown in open fields. For container growing, seedlings are raised indoors. Site is prepared by ploughing and levelling the land. Raised beds or ridges are prepared and later pits are made on these ridges to sow the seeds. Seeds are sown at a depth of 0.5 to 1 cm. Seeds are sown in pits which are spaced at 15-30 cm apart within a row. Row to row distance within a ridge is about 2.5 -5 cm. When plants are 10-15 cm tall, thinning is done keeping one plant for every 15-30 cm distance within a row. Plant to plant distance is kept more because of the spreading growing habit of the plant. Moist soil is preferred for New Zealand spinach growth. Soon after sowing seeds and thinning a light irrigation is given. On average the plants need to be watered at weekly intervals. While watering the plants, make sure that top 15-20 cm of soil is watered properly. After every harvest, watering is recommended to boost leaf production.
Since leaf production has to be promoted, application of liberal doses of nitrogen fertilizers are recommended. Farm yard manure or compost @40-50tons/ha may be incorporated into the top soil at the time of field preparation. After that a top dressing of 20 kilograms of nitrogen per hectare may be given after every harvest. For container growing, foliar application of a liquid nitrogen fertilizer is a good idea after every harvesting of leaves. Mulching may be done to retain soil moisture and suppress weed growth.
Plants are ready for harvest within 2-3 months after sowing seeds. Generally, terminal, succulent, lateral shoots are harvested for vegetable purposes. Harvesting may be continued for several months as and when new growths appear. Yield may vary between 2.5 – 3 tons per hectare per harvest. In other words, 2.5 kilograms of leaves may be harvested from one square meter area during one harvest. Annual yield is approximately 10-15 tons per acre of land.
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