Take care in the garden

Gillian Vine urges a little caution in the vegetable plot.

A Central Otago reader phoned to ask if we could highlight the dangers of the fruit of potatoes.

I don’t like the common name "potato apple" for the fruit, which looks like a green tomato, as it implies that it is edible. In fact, it is horribly toxic, thanks to the presence of solanine, a glycoalkaloid toxin which induces symptoms including dizziness, vomiting, diarrhoea, paralysis and even death. Removing the flowers of potatoes stops the fruit forming and doesn’t harm the crop.

The chemical is found in the foliage and green potatoes, too, although chlorophyll may be the cause of greening. Play it safe and don’t eat green spuds. Rather than waste them, pop them in the ground this month for a late crop of new potatoes, which will be quite normal and a treat for Easter.

Potatoes belong to the nightshade family (Solanaceae), which includes tomatoes, aubergines, chilli peppers and even tobacco. In some species, such as deadly nightshade (Atropa belladonna), the entire plant is toxic. Fortunately, deadly nightshade is rare in this country but black nightshade (Solanum nigrum), which is not as poisonous but still potentially harmful, is extremely widespread.

Another nightshade, poroporo (S. aviculare), has large berries that are poisonous when green, but the fully ripe fruit is edible. If you plan to eat poroporo, be certain of its identity as it can easily be confused with harmful nightshades.

Tomatoes also contain solanine, especially in foliage, stems and green fruit. Cooking reduces the risk, so green tomato chutney is a good way to use unripe fruit.

Solanine is not the only poison lurking in the vegetable plot. The oxalic acid in rhubarb is well-known and the leaves — where most is stored — are often used for a natural insect killer.

For a spray to zap chewing insects such as aphids, caterpillars and spider mites, put rhubarb leaves in a pot (ideally an old one no longer used for food), cover with water and boil for about 20 minutes. Allow to cool, then remove the leaves. Add a tablespoonful of dishwashing liquid, mix well and pour into a spray bottle. Clearly label the bottle "poison".

If you are thinning parsnips on a sunny day, make sure you wear gloves, or you risk getting parsnip rash (phytophotodermatitis), an unpleasant skin ailment that causes itching and blistering, usually about 24 hours after handling the vegetable. The reason for the rash is the presence of furocoumarins in the foliage and skins of parsnips, which in sunny weather interact with UV rays and set up the irritation. It is recommended that parsnips be peeled before cooking.

Celery and parsley have been known to cause parsnip rash, but seem to do so only occasionally.

Don’t let this doom and gloom put you off growing vegetables, as nothing tastes better than home-grown potatoes or ripe tomatoes warm from the sun.

Precautions

 - Teach children that if any plant or berry tastes nasty or makes the lips or mouth sting, they should spit it out at once — never swallow it — and immediately tell an adult. 

 - Keep the number of the National Poison Centre, 0800POISON (0800764-766), handy and contact the NPC if poisoning occurs or is suspected.