POISONOUS PLANTS IN NEW ZEALAND

New Zealand Journal of Agriculture, Volume 81, Issue 6, 15 December 1950, Page 551

POISONOUS PLANTS IN NEW ZEALAND

r y’HIS is the third section of a series of descriptions of poisonous plants which grow in New Zealand by H. E. Connor, Botanist, Department of Scientific and Industrial Research, Wellington. The series is appearing monthly in the “Journal”, and glossaries to be used with the series were published with the first section, which appeared in the October issue.

DICOTYLEDONS Thymelaeaceae Strathmore Weed. Pimelea prostrata (Forst.) Willd. (Fig. 5) Botanical description: Habit— Small, prostrate, or sub-erect, much branched shrub; branches up to 2ft. long. Leaves Small and crowded to laxly placed. Flowers— Small, waxy-white, in few or many flowered heads at the tips of the branches. Fruit white, ovoid berry. (New Zealand.) Habitat: Open pastures. Distribution: Abundant throughout New Zealand from sea level to 4500 ft. General: Poisonings caused by Strathmore weed are more common in horses than in other stock in New Zealand, though calves and yearlings have been known to be poisoned. Poisonings by this plant are not always fatal, but. the loss of thrift and the inability of the horses to work may be a serious setback to the farmer. From observations it appears that a tolerance can be built up against Strathmore weed, as horses have been known to recover from poisoning and then graze it occasionally without harmful effects. P. prostrata is often seen as the only green plant in dry pastures and is still untouched by stock, even during periods of shortage, of feed. There are a number of poisonous Pimeleas in Australia. Symptoms of poisoning: First symptoms in horses are marked depression, loss of appetite, and profuse watery diarrhoea. . These are followed by an intense inflammation and soreness of the mucous membranes of the mouth and tongue. The eye and eyelid become distinctly oedamatous and a yellow coloration is visible; at this stage a distinct weakening of the pulse is noticeable. Muscular pains and a strong. disinclination to move are prominent symptoms. Post-mortem examination symptoms of poisoning are available only from a fatal case in a horse. The undersurface of the tongue and the mouth showed small vesicles and circumscribed ulcers and a complete destruction of the epithelium. The mucous surface was distinctly yellow and acutely inflamed. In the stomach the lesions seen in the mouth were repeated. The intestines showed many infested areas but no marked lesions. The liver was undergoing fatty degeneration and was pale yellow. Poisonous principle: The toxin in P. prostrata is unknown, but it is possibly in the same class as the poisonous principle of daphne species, which is a narcotic irritant.

Coriariaceae Tutu. “Toot”. Tupakihi. Coriaria arborea Lindsay (Fig. 6) Botanical description: Habit — Shrub or small tree, with wide-spreading, 4angled branches, very variable in

POISONOUS PLANTS IN NEW ZEALAND

height, sometimes 25ft. tall. Leaves—--1 to 3in. long, ovate or oblong-ovate, prominently 3 to 5 nerved. Flowers— Many on long drooping racemes 4 to 12in. long or more; sepals and petals green. Fruit— Purplish black enveloped by the juicy, persistent, enlarged petals. (New Zealand.)

Habitat: Riverbanks, bush, scrub, and tussock grassland.

Distribution: Abundant throughout New Zealand up to 3500 ft.

General: Since the earliest records tutu has been responsible for the greatest percentage of plant poisonings of stock in New Zealand. Farmers claimed to have lost up to a quarter of their stock in the early days. Sheep and cattle are the animals mostly affected, as horses apparently do not eat the plant. Goats have been used to eat the plant down, thereby making it safe to run cattle on those areas. Cattle and sheep are also known to eat tutu without any ill effects, possibly because in normal grazing much other fodder is eaten with the tutu. Travelling, hungry stock are more readily poisoned than those which have been accustomed to tutu country. All parts of the plant except the soft, black, persistent petals are poisonous. Poisoning by tutu has been reported in man, and a recent outbreak of honey poisoning was traced to the fact that bees had worked honeydew produced from the sap of tutu.

Symptoms of poisoning: Convulsions and excitement, vomiting and defaecation, and exhaustion, precede a comatose state. Death follows, or may occur during the convulsions.

Poisonous principle: The toxin in tutu is tutin, which is allied to the picrotoxin group of poisonous substances.

Coriaria spp.

Other species of Coriaria have not had any specific poisonings attributed to them, but as C. sarmentosa Forst, f. was previously confused with C. arborea, and as C. lurida T. Kirk and C. angustissima Hook. f. have been shown to contain tutin, it seems reasonable to treat them as potential poison plants.