Beware the plants that poison

A new guide to poisonous plants has just been released, full of colour photos to help you identify the dangerous inhabitants on your lifestyle block.

Foxglove is one of the prettiest plants in a cottage garden and, arguably, around the lifestyle block. But it has a dark side that makes it undesirable to have on your property - it's poisonous. In fact, it's downright sinister.

It joins over 100 others in a book released last Friday titled Plants That Poison: A New Zealand Guide. It has been written by two of New Zealand's experts in this area. Henry Connor is a leading authority on poisonous plants and John Fountain is a medical toxicologist at the National Poisons Centre at the University of Otago.

The book is a timely reminder about which plants, trees and fungi to leave well alone. The outbreak of honey poisoning in the Bay of Plenty last year highlighted the need to be aware of the presence of poisonous plants in our environment - and in the country, there are plenty.

The danger exists not only to small children and the unwary, but also to stock. You simply cannot afford to throw garden weeds over the fence into the paddock where your animals can reach them. As plants begin the decomposing process, the sugar can increase in them, making them more palatable and therefore more tempting to eat, especially if stock are running short of other food.

The nightshade or Solanum family of plants includes potatoes, tomatoes, aubergines, chillies, capsicums and tobacco as well as many others. The plant that is the subject of most inquiries to the National Poison Centre is the black nightshade; in particular, its berries.

While mistakenly called deadly nightshade by many, that plant is rare in New Zealand. The black nightshade plant is common and grows in gardens, waste places and amid farm crops throughout the country. It seems to grow particularly well where the ground has been disturbed.

The most common variety, S. nigrum, grows berries from the clusters of small white flowers and these change from green to purplish black.

The whole plant is poisonous, but the berries are the most toxic. Signs and symptoms include fever, sweating, vomiting, abdominal pain, diarrhoea, confusion, hallucinations and stupor. These usually appear six to 12 hours after ingestion.

"Keep children away from them," Dr Connor advises.

The NPC recommends people contact it if more than three unripe or six ripe berries are eaten or if any symptoms occur.

While not wanting to frighten people into cutting down or pulling out all the potentially nasty trees, shrubs and garden plants, the book contains over 100 colour pictures to help people identify the poisonous plants they live with.

"Small children are vacuum cleaners," Dr Connor says, "everything goes up towards their mouth and we want parents, in fact any caregiver, to be sure of what they're talking about; that's why the pictures are there."

S. dulcamara, or bittersweet, grows in shady places in scrub and forest margins and the berries are again the most toxic part of the plant. S. aviculare and S. laciniatum are also known as poroporo. These are two native shrubs usually found in lowland forest or scrub and sometimes in gardens. It is the unripe fruits of both these plants that have the reputation of being poisonous, "though they seem safe when ripe", Dr Connor says.

Boxthorn hedges are a familiar sight on farms in Taranaki. This small tree bears red berries protected by the sharp spines it is famous for. Boxthorn is poisonous more by reputation than by established fact.

The knowledge of the toxicity of karaka berries, however, has long been handed down through Maori knowledge and custom. It is the fresh fruit that is poisonous, causing violent muscular spasms and eventual death. But the kernels are processed in a way, through particular washing and baking, to make them useful as a "source of floury food" the book says. "Karaka berries have become part of modern Maori cuisine, but they are baked before being offered at dinner."

Tutu is the plant at the centre of the honey-poisoning incident in 2008. It is the most important native poisonous plant in New Zealand. During early settlement, stock losses to this plant were a major problem and it is still a threat to them, especially to cattle.

"Whether a tree or a shrub, it makes no difference to animals grazing wild tutu plants in scrub, or along roadsides, or in riverbeds. They die," Dr Connor says.

Broom is a pest plant found along roadsides and in paddocks and all parts are toxic. Lupin is the same, but the toxins are particularly found in the pods and seeds.

Hemlock shouldn't be handled without gloves and is a time- honoured poisonous plant (Socrates famously died by ingesting it).

It can be mistaken for parsley or carrots by children and for culinary fennel by adults. It can grow up to two metres tall with purple speckling of the green stems.

The leaves are like carrot leaves and the white flowers grow in flat-topped clusters. This poisonous plant grows in waste places, often beside streams and can cause respiratory and renal failure among other things.

Plants That Poison is a must- have book to take with you around your garden and farmland, with your children in hand, to educate yourselves and them about which plants are not to be touched. Included in it is a section on mushrooms and fungi, which is particularly relevant at this time of year.

Plants that Poison: A New Zealand Guide, by Henry Connor and John Fountain (ISBN: 9780478093988) is available from bookshops or from Manaaki Whenua Press, PO Box 40, Lincoln 7640, or see the website at, or phone (03) 321-9662.

* Got a lifestyle block story or simply want to get in touch with Vicki Price? You can write to her c/- Features editor Deborah Sloan, 49 Currie St, PO Box 444, New Plymouth 4340, or ring the newspaper on 759-0800 ext 8705#, or email with Vicki Price in the subject line.

Taranaki Daily News