When I was young, I always wanted to grow spinach (Spinacea oleracea) in Singapore. Due to the fact that it is a cool-growing crop, it would not thrive. After looking up various vegetable gardening books, I was introduced to various warmer-growing spinach alternatives, one of which was the New Zealand spinach, which is also known as the warrigal cabbage/greens in Australia. Botanically known as Tetragonia tetragonioides, the New Zealand spinach is a day-neutral and salt-tolerant member of the Aizoaceae family. The edible parts of the plant are rich in vitamin A, vitamin B1, vitamin B2, vitamin C content but low in fiber. In Singapore, New Zealand spinach is not commercially for sale.
From various resources, it is documented that the New Zealand spinach is a xerophyte which is capable of tolerating long periods of drought. In the lowland tropics like Singapore, New Zealand spinach is said to be more suited for growing in the cooler highlands. I managed to grow some here, but I notice it only thrives if given filtered sunlight as it tends to suffer from severe heat- and moisture-stress if grown under full sun. When that happens, the leaves turned yellow and remained small. Growth of the plant virtually halts to a stop. I grew my plants in a well-draining but fertile soil that is kept moist at all times. I also applied regular doses of liquid fertiliser to encourage rapid and tender growth.
Under such a cultivation regime, the triangular leaves of the New Zealand spinach I grew seems to be still quite small compared to the reported size – 10 cm in length and almost 8 cm wide. Plants adopt a trailing and vining habit. They also produce small, yellow flowers as reported. Growth seems to be a bit sluggish, probably due to the lowland heat. I also noticed that it can die away during the extreme hot months in Singapore from April to July.
According to Plant Resources of Tropical Africa (PROTA), it is reported that harvesting can commence once plants have grown to a height and length of over 30 cm. Tops up to 20 cm may be cut for the first harvest. Avoid picking older growth with fruits as they would have become bitter and fibrous. Regular harvests help to promote branching but with time and numerous harvests, plants can become ‘tired’ and the crop is then removed when the yield and quality have become inferior.
At present, I have not attempted to harvest the young shoots for consumption. New Zealand spinach should not be eaten raw as it contains calcium oxalate crystals, although many people still use it raw in salads. The edible portion needs to be cooked to destroy them by blanching them for at least 3 minutes where the cooking water is disposed of and the greens refreshed in iced water before eating.