Avoiding the danger of menacing plants

Some plants don't have to be eaten to cause problems, such as ongaonga, which has tiny toxic hairs on its leaves. Photo / Supplied

In Auckland Museum's exhibition The Poisoners experts look at toxic surprises that may lurk in the bush or the bathroom. In part three of a series we look at poisonous plants.

Hemlock takes an annual toll on livestock but, like most poisonous plants, poses limited risk to people unless it's ingested.

Museum botany curator Ewen Cameron says as a young plant, hemlock looks like a fern with finely divided green leaves. The mature plant has hairless, purple-blotched stems that can grow to over 2m with clusters of white flowers at the top. Ingesting hemlock can cause nausea, vomiting, respiratory or renal failure, seizures, coma and even death.

New Zealand has its share of poisonous natives including the yellow seeds of the kowhai, the kernels of karaka berries, the green fruit of the poroporo shrub and the leaves of the ngaio tree. Eating their seeds or fruit might leave you with nausea, vomiting or violent headaches.

Another common toxic native around streams and roadsides is tutu, which has glossy leaves and dangling flowers and fruit.

Every part is toxic, affecting the nervous system if eaten leading to shock and convulsions. A plant that doesn't need to be eaten to cause problems is the native ongaonga or tree nettle, found around margins of bush mainly south of Auckland. It's a woody shrub with needle-like stinging hairs that give off a poison when brushed against.

The National Poisons Centre says the most childhood poisonings involve arum lily, black nightshade, euphorbia, iris, oleander, agapanthus, ongaonga, hemlock, foxglove and rhus.

"The rule is if you don't know what it is, don't eat it," says Cameron.

In an emergency

* Get medical help immediately. Do not induce vomiting or offer excessive fluids.

* Phone the New Zealand National Poisons Centre on 0800 POISON (0800 764 766) - this toll-free service operates 24 hours a day.