Thursday, October 23, 2008

Native Spinach

Tetragonia tetragonioides
This is a fast-growing, prostrate annual plant which grows very easily from the hard, prickly seeds. It is quite likely just to come up in your garden, as it did in mine, brought by birds, no doubt. It is a nutritious and tasty no-cost vegetable, which, once established provides leafy greens for much of the year with no further help from the gardener. It’s worth putting aside a well-composted space in the vege garden, one or two metres square, for it to ramble and reseed at will. It appreciates a bit of water in very dry times, but doesn’t really need it.
Discovered in 1770 by the botanists on Captain Cooks’ famous voyage, this plant was named by them “New Zealand Spinach”. After leaving New Zealand, they sailed to Australia, and found the same plant growing here. Cook was one of the first sea captains to recognise the scientific discovery that, scurvy was caused by a lack of something - now known to be vitamin C - in fresh fruits and vegetables. The value of this plant as a health food was quickly recognised. The officers tried it and pronounced it “as good as spinage”. (The knowledge that they enjoyed it with a dish of stingray tripe does, I’ll admit, reduce one’s confidence in their taste.) They carried the seeds back to England where it became what is still a popular summer vegetable. Known there as “tetragon”, it is considered to have a flavour superior to spinach and silver beet.
Twenty years later, the first white settlers at Sydney Cove were having trouble finding enough food to stay alive. Saturdays were set aside for collecting native plants to eat, especially those which could prevent scurvy. Tetragon was one of the plants collected. It lost favour early on, however. In a colony nostalgic for the homeland, the prejudice in favour of “real English spinach” couldn’t admit that a “weed” from the bush might taste better!
The modern bushfood industry calls this plant “Warrigul Greens”.
Leaves should be washed, chopped (or roll them up and slice them finely), and lightly cooked. Butter, salt and pepper is all that’s needed for a delicious vegetable, but native spinach is also good added to a creamy pasta sauce, included in a risotto, or cooked into a quiche. Another recipe serves it in a white sauce with chopped boiled egg and nutmeg. An imaginative cook will have no trouble finding a good many ways to serve this versatile vegetable!
There have been some concerns about the safety of this plant because it contains oxalic acid, which can be harmful to humans.

How dangerous is Oxalic Acid?
A number of Australian plants with edible leaves have high oxalic acid levels, and are avoided for this reason. Taken in excess, oxalates are poisonous substances which can cause nausea, vomiting, corrosion of the digestive tract, and sometimes, death. Frequent use can also cause calcium deficiency and kidney stones.
However, to put the issue into proportion, we should bear in mind that oxalic acid occurs in all green leaves, and that we already eat a lot of plants that are high in it.
The amount contained in native spinach (Tetragonia tetragonioides) is approximately the same as in “English” spinach, and a little less than in silver beet.
Many of the everyday herbs which we grow, or buy in the supermarket, are very high in it. French cooks couldn’t manage without a pot of sorrel (Rumex acetosa), which an internet sales source describes as having “a lemony tang that’s almost as sour as rhubarb”. It’s the high level of oxalic acid that provides the sourness.
It actually takes quite a lot of it to cause harm. Ill effects are typically found only when consumption is very high (more than 12 cups of cooked leaves a week). This is the sort of consumption which occurs in poor, third-world communities where a belly-filling feed is hard to come by.
Some writers claim that high-oxalate vegetables should only be eaten after a cooking process involving blanching them in boiling water for a minute - and this is certainly a way to make them safe, if you think you might be feeding the family too much of it. Most of the oxalates dissolve easily into the water, which is then discarded. Others consider that a certain amount can be eaten safely in recipes where no cooking water is discarded, and salads. The popular spinach quiche would be an example of a relatively high-oxalate meal often eaten in Australia.
A diet high in oxalate-rich leaves should also include high calcium intake, which may offset the tendency to form kidney stones. Typical recipes involve milk, yoghurt, or cheese.

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