POISONOUS PLANTS IN NEW ZEALAND

New Zealand Journal of Agriculture, Volume 81, Issue 4, 16 October 1950, Page 317

POISONOUS PLANTS IN NEW ZEALAND

THIS article introduces a series of descriptions of poisonous plants which grow in New Zealand by H. E. Connor, Botanist, Department of Scientific and Industrial Research, Wellington. They will be accompanied by 26 illustrations. Readers who are likely to find the series of interest should retain the glossaries printed in this issue for use with the descriptions and illustrations of plants to appear in subsequent issues of the "Journal".

HERBIVOROUS animals on free range indulge a wide and varied taste in the plants they eat as fodder. Their taste, however, does not always lead them to distinguish between plants that are safe and useful as fodder and plants that are poisonous. Many plant associations include at least some species injurious to stock, and in consequence grazing animals are often exposed to the risk of harm from eating these species. The risk is greater when animals range over large tracts of land on which the herbage is subjected to very little control by man, and is increased still further when the native flora includes a large number of poisonous plants. _ As more restraint is placed on the animals by subdivision of the grazing areas, and, particularly, as the herbage itself is controlled by the planting of desirable pasture species and by intensive care and management of the crops, so does the risk of poisoning by plants become correspondingly reduced. '

Among farming countries of the world New Zealand is relatively fortunate in the number of stock lost from poisoning by plants. A considerable proportion of the stock is grazed under a system of intensive management which normally keeps the

pastures free from invasion by toxic plants. The remaining stock on the relatively extensively 'managed hill country and on the extensively managed highlands are not exposed to as great a number of poisonous native species as are those in some other lands. Losses from plant poisoning are nevertheless appreciable and constitute a steady, if small, drain on the resources of the farming industry and on the profits of the individual farmer. Even intensive management of pasture may sometimes fail to give protection against invasion by toxic plants: For example, heavy growths of the poisonous variegated thistle may occur in pasture swards debilitated by drought; adverse weather may temporarily change pasture to a toxic state capable of producing facial eczema in stock; on extensively managed areas introduced ragwort has become estab-

fished and presents a difficult problem of control; and the native tutu still exacts its toll of animal life.

This series of articles comprises part of a very full and detailed survey of the known poisonous plants, both native and introduced, that occur in New Zealand. Information has been gathered from many z sources—from personal observations, from the records in the archives of Government ' Departments, and from Unpublished literature of New Zealand and of countries overseas. Added value has been given by the cooperation of numerous men in the field —Government Veterinarians. Instructors in Agriculture, and Inspectors of Stockwho have supplied particulars of the distribution of poisonous plants and of symptoms and the incidence of stock poisoning in their districts. Analysis of. such data supplied in answer to a questionnaire has been in itself a not inconsiderable task. No information was avail--11 able about the effects of many native plants on animals, and experimental feeding work on samples collected by the author was carried out at the Department of Agriculture Animal Research Station, Wallaceville. The result is a valuable conpoisonous plants. It. is a

tnbution to knowledge of comprehensive reference to wmcn to turn wnen siock losses have occurred, but, still more important, it can be of signal value in preventing loss of stock. In general, avoiding loss entails preventing access of stock to poisonous plants. It means eradication and destruction of poisonous plants, fencing off of areas growing toxic plants, and careful disposal of poisonous clippings or trimmings. For all such work recognition of poisonous plants is a necessary preliminary; the descriptions and illustrations in these articles will enable such knowledge to be acquired. Only when the information is used to prevent stock losses will it achieve its purpose fully.

—I. J. CUNNINGHAM,

Superintendent,

Department of Agriculture Animal Research Station, Wallaceville.

GLOSSARY OF BOTANICAL TERMS

A Achene— small, dry, hard, indehiscent, one-seeded fruit, as in buttercups. Acuminate — a gradually diminishing point. Acute—Sharply pointed. Annual— cycle completed in 1 year. Auricle small lobe, an appendage to a leaf; hence auriculated. Awn— bristle-like appendage, as on the glumes and lemmas of grasses. Axillary Occurring in the axil, as between stem and leaf. B Berry—A pulpy fruit with immersed seeds. Biennial—Flowering and dying in the second year. Bulb —A short root stock, with the buds covered by fleshy leaf scales. C Calyx The outer floral envelope, sepals. Campanulate shaped, as of a corolla. Capsule Dry, dehiscent fruit. —Broadly notched at the base, as of petals and leaves. Corolla The inner floral envelope, petals. Corymb— inflorescence with flowers arising at different levels to form a flattish top; hence corymbose. CrenateScalloped, or with rounded teeth, as of leaves. , Culm—The stalk of sedges and grasses. Cuneate—Wedge shaped, as of leaves, petals, sepals. CupuleThe cup of such fruits as an acorn; hence cupular. D Deciduous Falling after completion of function, as of leaves. Decompound— divided, as of leaves. DecumbentProstrate with ascending tips, as of stems. Deflexed downward, as of sepals. —Toothed, with the teeth outwardly directed, as of leaves. —The central part of the head in composite flowers, on which the disc florets are situated. The receptacle. Drupe—A fruit of three layers, an outer skin, a fleshy layer, and a hard inner layer, as in a plum. E Elliptic Oblong with regularly rounded ends, as of leaves. Emarginate—Notched at the free end, as of leaves. Ensiform —Sword shaped, as of leaves. F Falcate —Sickle shaped, as of leaves. FiliformThread-like, as of florets in Compositae. Flexuousßent in a zigzag or wavy fashion. FloretA small flower, as of Compositae. Follicle —A fruit of one carpel, opening along the inner margin, as of delphinium. G GlabrateLacking pubescence, or nearly so; hence glabrous. Glaucous—Covered with bluish bloom, as of leaves. Globose— spherical. Glume—Chaffy outer scale in the spikelets of grasses. ... |_| Hermaphrodite— sexes in one flower. I Overlapping, as of leaves or floral " parts. Inflorescence flowering portion of a plant.

InvolucreA series of bracts surrounding a . group of flowers or their stalks, as of Compositae; hence involucral. I —Blade of leaf. L —Tapering toward each end, with the greatest breadth about one-third way up, as of leaves. • Lemma outer husk of a grass floret. Lenticel —A corky spot on young bark, as in elder. Ligule—(a) The strap-shaped floret in Compositae; hence ligulate. (b) The projecting portion at the junction of sheath and blade in grasses. Linear Narrow, several times longer than wide, as of leaves. ■■/ ■ Pinnately lobed, with a large terminal lobe and smaller lower lobes ; hence lyratopinnatifid. kJ Membranous Very thin, more or less ’’ translucent, as of leaves. < MucronateSharply pointed, as of leaves. Mycelium vegetative portion of a fungus; hence mycelial. KI Node The place of insertion of a leaf or I '' leaves. Nut —A hard, indehiscent, one-seeded fruit. r'N Oblanceolate — for lanceolate, but the widest part in the upper third. Obovate—Reversed ovate, widest part toward the apex, as of leaves. Obtuse—Rounded at the apex, as'of leaves. Orbicular Circular or nearly so in outline, as of leaves. Ovate—Egg shaped in outline, the broad part at the base. Ovoid—Egg shaped, as of fruits. D Palmate—Lobed in the manner of the r fingers of an open hand, as of leaves. Panicle indeterminate inflorescence, in which the axis divides several times; hence paniculate. PapilloseCovered with soft, superficial glands or protruberances. —Divided, but not quite to the base, as of leaves. Pedicel —Supporting stalk of a single flower, as in a compound inflorescence. Peduncle The stalk of a flower or a cluster of flowers. Pendulous — Perennial Lasting several years, as opposed to annual or biennial. Perianth floral envelope; usually applied when the calyx and corolla are similar, or one is absent. Petiole Stalk of a leaf. Phyllary—An individual bract of the involucre of a composite flower head. PiloseHairy. Pinna — of a pinnate leaf; hence pinnate, pinnately. Pinnatifid —Pinnately cut half-way to midrib, as of a leaf. —Pinnately cut down to midrib. Procumbent along the ground, as of stems. Prostrate Flattened to the ground, as of stems. PuberulousSlightly hairy, . Pubescent in soft, short hair.

D Racemelndeterminate inflorescence, with • ' primary axis bearing pedicelled flowers. Radical-Arising from the crown of root stock, as of leaves. Ray— ligulate marginal floret as in Compositae. Receptacle The part of the floral axis bearing the envelopes and sexual organs. Recurved backward. RhizomeA spreading underground stem. Rhomboid —Lozenge shaped; hence rhomboidal, as of leaves. RotateOf a corolla with a very short tube and regular, spreading lobes. SScabrid— Rough to touch, as of leaves. Scape—Radical, leafless, floral axis or peduncle. Sclerotium —Fruiting body of a fungus, as of ergot. . Serrate With sharp, forward-pointing teeth, as of leaves. Sessile— a stalk, as of leaves. SinuateWith a wavy margin, as of leaves. Sori —Asexual reproductive organs of ferns. Spathe large bract enclosing a flower cluster, as of monocotyledons. Spathulate—Oblong with base drawn out like a spathula. SpikeletsThe separate flower clusters in grasses and sedges. Spine—A sharply pointed woody organ; hence spinose. Stellate—Star shaped, as of hairs with radiating branches. —The leaf stalk of a fern. StipuleAn appendage to a leaf at or near its insertion on the stem. Stolon spreading and rooting overground stem; hence stoloniferous. Striate—Masked, with fine parallel lines, as of leaves. Sub —Prefix meaning somewhat; hence subprostrate, subacute, suberect, subsessile, subcompressed, subpaniculate, suborbicular, subglobose. Subulate— shaped, as of petals and sepals. Succulent —Juicy. T Tendril —Modification of a leaf or stem acting as a climbing organ, as in sweet peas. Tepal— member of a floral envelope in which sepals and petals are similar or not clearly distinguishable, as of Polygonaceae. Terete —Circular in section. Tomentum —A dense covering of woolly, matted hairs; hence tomentose. Trifid—Three cleft. Trifoliate — leaved. Trigonous angled, as of culms in some sedges. Tripinnate— pinnate. Truncate Ending abruptly, as if cut off. TunicateHaving coats or tunics. U Umbel inflorescence with a cluster of pedicels arising at the same point; hence umbellate. Undulate Wavy, as of margins of leaves. Unisexual—One sex present in flower. Utricle —A membranous covering to the fruit, as in Carex. y Villous— long weak hairs. W Whorled Organs arranged in a circle around the axis.

Poisonous Plant Defined

In general terms, a poisonous plant is one which when eaten by animals exerts harmful effects or produces death because of its toxic substances.

Types ,of Poisoning

Sublethal: Produces a condition of debility or sickness.

Lethal: Produces death

The word toxic is used broadly to cover, in some cases, both sublethal and lethal.

Classification of Poisonous Plants Of the methods available for the

classification of poisonous plants the most commonly used are: —

1. Natural grouping of plants into families.

2. Nature of the toxinfor example, alkaloid or glycoside.

3. Physiological action of the toxin—for example, irritants or blood poisons.

4. Part of the plant eaten.

Of these four the botanical method of separating the plants into families is the most readily applicable, as it avoids the overlapping which occurs if any of the other methods are employed. This botanical type of classification is used in this series.

Poisonous Principles

The poisonous plants of New Zealand contain toxins which are recognised all over the world as causatives of poisonings. There are five main categories: — -

1. Alkaloids, which are complex nitrogenous substances synthesised by plants. They are not all toxic. Some of the plant families which contain alkaloids are Papaveraceae, Monimiaceae, Solanaceae, Papilionaceae, and Compositae.

2. Glycosides, which yield on hydrolysis sugars and one or more other substances, the aglycones.

(a) Cyanogenetic glycosides: These substances liberate hydrocyanic (prussic) acid (HCN) in the presence of a suitable enzyme. Crushing of leaves may be sufficient to bring the enzyme and the glycoside into contact. Two of the plants containing cyanogenetic glycosides which grow in New Zealand are linen flax (Linum usitatissimum) and titoki (Alectryon excelsum).

(b) Other glycosides: Two plants containing glycosides are foxglove (Digitalis purpurea) and karaka (Corynocarpus laevigata). Saponins are present in some poisonous plants, but their toxicity is not pronounced. Mustard-oil glycosides are to be found in members of the Cruciferae.

3. Photodynamic substances, which occur in plants which cause photosensitivityfor example, St. John’s wort (Hypericum perforatum).

4. Inorganic compounds: Nitrates accumulated by plants may be broken down by bacterial or enzyme action into toxic nitrites. Plants associated with this type of toxin are mangolds (Beta vulgaris var. rapa) , hay made from oats (Avena sativa) , and variegated thistle (Silybum marianum) . . 5. Other substances: Tutin present in tutu (Coriaria arborea) is a picrotoxinlike substance. Oxalic acid is the toxin present in such plants as sour dock (Rumex acetosa) and Bermuda buttercup (Oxalis cernua) . False acacia (Robinia pseudacacia) and castor-oil plant (Ricinus communis) contain phytotoxins. Physiological Action of the Poisonous Principle 1. Blood poisons: Castor-oil plant (Ricinus communis) and false acacia (Robinia pseudacacia). 2. Neurotic poisons: Opium poppy (Papaver somniferum), and henbane (Hyoscyamus niger). 3. Neuro-muscular poisons: Foxglove (Digitalis purpurea). 4. Irritants: Brassica species and Ranunculus species. Conditions Influencing Plant Poisoning There are characteristic well-known conditions of plant poisoning; these are mentioned throughout the series where they occur specially, but are generalised here to serve as a guide:— Condition of the Plant Part of the plant: A specialised part of the plant may be poisonous while the remainder when eaten will cause no toxic effects, or some part of the plant may be more toxic than any other part. The poisonous properties of some crucifers are restricted to the seeds, and there is an accumulation of toxic amounts of alkaloid in the seeds of some Leguminosae. Karaka is a well-known instance in which the kernels of the drupes are the only poisonous part of the plant and only when they are eaten fresh or raw. Stage of growth: Into this group falls the example afforded by poroporo (Solanum aviculare), of which the green berries are poisonous and the ripe berries are not. Some buttercups (Ranunculus spp.) increase in toxicity up. to flowering time, when they are most toxic, and decrease in toxicity after maturation.

Soil conditions: The presence in the soil of quantities of the selenium which is absorbed by certain plants leads to poisonings in certain parts of the United States of America. Some plantsfor example, variegated thistle (Silybum marianum) cause poisonings by the quantity of nitrate absorbed from the soil. Lantana (Lantana camara) is known to vary in toxicity with soil changes, as in Australia.

Condition of the Animal

Travelling stock are those most frequently poisoned, as they are forced by circumstances to eat plants to which they are not accustomed or to eat more than they might normally. The rapid absorption of the toxins in an empty stomach may be the cause of the frequent poisonings in hungry stock.

Symptoms of poisoning which develop only when animals are forced to move are exhibited after the consumption of such plants as mallow (Malva parviflora) and woundwort (Stachys arvensis).

Animals with white skins or weakly pigmented areas of skin develop photosensitivity diseases after eating plants which contain photodynamic substances. When the animals are subjected to light, photosensitivity diseases result. The external symptoms of these diseases are not seen in stock with black or heavily pigmented skin. One of the vagaries of domestic animals is the eating of cuttings or clippings of plants which they might not eat during normal foraging. Glossaries and Synopsis Glossaries of botanical and veterinary terms used in this series appear on pages 318 and 320 and should be used for reference during the currency of the series in the “Journal”. They should be of assistance in both the use of the botanical descriptions and in the discussion of symptoms of poisoning. The place name at the end of a botanical description indicates the country of origin. A synopsis of the grouping of the plants into , three classes and a classification of the plants mentioned in the text into trees, herbs, and shrubs will be published at the end of the series. ' Acknowledgments In addition to the assistance of officers of the Department of Agriculture previously mentioned, others whose work is acknowledged are staff of the Botany Division of the Department of Scientific and Industrial Research and C. W. Brandt of the Dominion Laboratory. Reference List Following is a list of the main texts and papers on poisonous plants in New Zealand. Constant use has been made of these publications in the preparation of the text and they may be used with advantage in association with this series of articles: — Aston, B. C: "The Poisonous and Suspected Plants of New Zealand”, “The New Zealand Journal of Agriculture”, volume 16 (1918), page 324; “The Poisonous, Suspected, and Medicinal Plants of New Zealand”, "The New Zealand Journal of Agriculture”, volume 17 (1918), page 6, and volume 26 (1923), pages 78, 149, and 230. , Hurst, E. (1942): “Poison Plants of New South Wales”, Sydney. Long, H. C. (1917): "Plants Poisonous to Livestock”, Cambridge University Press. Muenscher, W. G. (1939): "Poisonous Plants of the United States”, New York. Nicholson, J. A. (1945): “Lander’s Veterinary Toxicology”, London.

Pammel, L. H. (1911): “Manual of Poisonous Plants”, Cedar Rapids, lowa.

Steyn, D. G. (1934): “The Toxicology of Plants in South Africa”, South Africa.

DICOTYLEDONS

Monimiaceae Pigeonwood. Porokaiwhiri. Hedycarya arborea. Forst. (Fig. 1) Botanical description: Habit—tree 20 to 40ft. high; trunk up to 20in. in diameter. Leaves Opposite, 2 to sin. long, coarsely toothed, tough, dark green above and paler beneath. Flowers — Small, in clusters, white green in colour. Fruit Drupes, clustered, fleshy, turning bright red when ripe, jin. long. (New Zealand.) Habitat: Throughout bush and around bush edges. Distribution: Abundant from North Cape to Banks Peninsula and Milford Sound. Sea level to 2500 ft. General: In feeding trials conducted at the Animal Research Station, Wallaceville, pigeonwood has proved to be lethal to sheep and non-lethal to cattle. It was originally reported as a suspect in a case in which several cows were poisoned fatally. On the basis of field observations, one investigator pronounces pigeonwood to be palatable to sheep, which were found to have grazed on young plants. No mention was made of toxicity. The . plant material used in the feeding trials was collected from adult plants which possibly are more poisonous than the juvenile ones. The adult plant foliage is not normally accessible to stock, but the leaves of immature plants may be; storms may make adult foliage available by breaking down branches. Symptoms of poisoning: Experimental cases showed that in sheep there was dullness, anorexia, and loss of weight. No marked post-mortem lesions were visible. In a cow there was loss of appetite and a good deal of depression; on post-mortem examination no changes were visible. Poisonous principle: The presence of an alkaloid in the plant is indicated by chemical methods.

GLOSSARY OF VETERINARY TERMS

A AbomasumThe fourth stomach of a ruminant. —Absence or loss of appetite. Asphyxiation—Suffocation. —Loss of- power ,of muscular coordination. Atrophied— in size and function; wasted. ,O Blind gut—The Caecum. ♦ '*■' Buccal—Relating to the cheek. C Caecumßlind gut on part of the alimentary canal. •Catarrhlnflammation of the mucous membrane. Cathartic Purgative. . Chorealnvoluntary muscular twitching. Cirrhosis Hardening of tissue. Clonic —Related to convulsions marked by alternate rigidity and relaxation of the muscles. Colic Acute pain in the stomach. Coma Stupor; abnormally deep sleep. Congestion Abnormal accumulation of blood in a part of the body. Conjunctiva—Membrane lining of the eyelid. Cyanosis— or purplish discoloration of the skin and mucous membrane. f) Dermatitis—lnflammation of the skin. Diuretic medium increasing the flow of urine. DyspnoeaDifficult breathing. C Eczema —An inflammatory condition of the u skin. Emaciation —A wasted condition of the body. —Vomiting.

—lnflammation of the intestine. Enuresislnvoluntary passing of urine. Epileptiform— in severe and sudden paroxysms. G Gangrene Death and putrefaction of a part. Gastro-enteritis —Inflammation of the stomach and Intestines. HUaematuria — blood cells in urine. Haemoglobinßed colouring matter of blood. Haemoglobinuriaßlood colouring matter in urine. Haemorrhagicßleeding. Hoven —Bloat. HyperaemiaCongestion. Excess of . blood In any part of the body. j Icterus jaundice; hence icteric. J Jaundice Yellowness of the skin, fluids, and tissues caused by presence of the bile pigments. | Lactation —The secretion of milk. M Methaemoglobin— product of the ox Ida- •** dation of blood colouring matter. Mucosa —Mucous membrane. Mucous — to mucus. Mucus —Slimy substance secreted by the glands of the mucous membrane. N Narcotic— drug which produces sleep or stupor, thereby relieving pain. Nausea Feeling of sickness. & . .

Necrosis —Death of a group or groups of cells —lnflammation of the kidney. OedemaSwelling produced by large quan titles of fluid in the tissues. • P ParoxysmA fit. A recurrence or intensl * flcation of symptoms. Peritoneum Membrane lining the abdominal cavity; hence peritoneal, peritonitis. Photosensitivity—Sensitive to light; hence photosensitisation. Pleura —The serous membrane lining the thoracic cavity and covering the lung. D Rectum—Terminal portion of the digestive •' tube. Rumen Paunch of a ruminant 0 Salivation Production of unusual secretion J of saliva. ' • ■ SerosaSerous membrane. StertorousCharacterised by snoring T Tetany—Spasm of many or all voluntary • muscles. Trifoliosis produced by Trifoliwr. species. Tympanites—Distension of the abdomen by gas |J Ulceration Open sore other than a wound V Venous Applied to blood returning to the “ heart after circulation in the body. VesicatoryCausing blisters. Viscera internal organs contained in various parts of the body.