Journal of the Department of Agriculture, Western Australia, Series 4

Volume 8 Number 2 1967 Article 2

1-1-1967

Poison plants of Western Australia : the toxic species of the genera Gastrolobium and Oxylobium. 1. Characteristics of the group

T E H Aplin

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Recommended Citation Aplin, T E H (1967) "Poison plants of Western Australia : the toxic species of the genera Gastrolobium and Oxylobium. 1. Characteristics of the group," Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 8 : No. 2 , Article 2. Available at: https://researchlibrary.agric.wa.gov.au/journal_agriculture4/vol8/iss2/2

This article is brought to you for free and open access by Research Library. It has been accepted for inclusion in Journal of the Department of Agriculture, Western Australia, Series 4 by an authorized administrator of Research Library. For more information, please contact [email protected]. POISON PLANTS OF WESTERN AUSTRALIA

The toxic species of the genera Gastrolobium and Oxylobium

1. CHARACTERISTICS OF THE GROUP

By T. E. H. APLIN, B.Sc, Botanist

THE toxic species of the genera Gastrolobium and Oxylobium are a unique group of poison plants which have caused considerable economic loss to stock-raisers in Western Australia ever since the early days of settlement.

These plants are widely distributed over being toxic have been shown to be harm­ the agricultural areas of the south-west, less to stock, and have been placed in and, with the opening up of large tracts other sections or genera. Roe's poison and of land for stock-raising, the danger is as net-leaf poison, previously classified in high as it has even been. Considerable other plant groups, are now placed in the losses of stock are still being sustained by section Podolobium of the genus Oxy­ farmers and graziers, due to accidental lobium. grazing of these plants. Description Botanical relationship The following characters, although not The genera Gastrolobium and Oxylobium completely reliable, serve in most instances belong to the pea-flowered, pod-bearing to describe the toxic pea-flowered plants: family, the Papilionaceae, and to the tribe Podalyriae, the members of which possess flowers in which the ten stamens are all distinct and separate. In this they are distinct from the other tribes, Genis- tfae, Trifolieae, Loteae, etc., in which all ten stamens are united or nine are united with one free. Only the species belonging to the section Racemosae in the genus Gastrolobium and to the section Podolobium in the genus Oxylobium are toxic. Several species which had previously been suspected of 42

Journal of Agriculture, Vol 8 No 2 1967 1. All are shrubs, that is, they branch close to ground level, and possess woody This is the first in a series of articles stems. Most are less than 5 ft. high, the on the toxic species of the genera Gas- exceptions being box poison, heart-leaf trolobium and Oxylobium, the most poison, river poison, narrow-leaf poison, important group of poison plants found rock poison, Roe's poison, and some forms in Western Australia. of prickly poison, which may sometimes In these articles great stress is laid reach 10 ft. in height. on the serious hazards presented by these plants. Characteristics by which they may be 2. The leaves are opposite to each other identified are set out in detail. Their on the stem, or in whorls of three, four distribution and the type of country or more. Rock poison has leaves irregularly where they are likely to be found is arranged. Narrow-leaf and berry poison also indicated. have crowded leaves which, while usually Subsequent articles in the series will in opposites or in threes, may sometimes deal with individual members of the be irregularly arranged. Box poison has group in turn. leaves that are arranged in opposites or threes but sometimes scattered.

that they persist even after the leaves have fallen. In most other species the stipules are small and bristle-like. In rock poison they are deciduous so are rarely seen. In York Road poison, the stipules are rigid and spreading.

4. The flowers are arranged in loose spikes on an inflorescence-stalk or ped­ uncle, with each flower attached to the ped­ uncle by a flower-stalk or pedicel. The flowers and pedicels are arranged on the peduncle in similar fashion to the leaves of the main stem (in pairs, threes, fours, etc.). The racemes are terminally arranged at the ends of branches or from the axils of uppermost leaves along the stem. They are usually longer than the leaves, and so 3. At the base of each leaf, one on protrude above the foliage. Heart-leaf either side of the leaf base or the leaf poison and narrow-leaf poison are notable stalk, are two small organs, the stipules. exceptions; in these the racemes are con­ In gilbernine poison and mallet poison, tracted, so as to appear short and broad. these are flat, lance-shaped, rigid and joined to the leaf stalk at the base, so

43

Journal of Agriculture, Vol 8 No 2 1967 5. The calyx (the outer green series of 8. The ten stamens are all distinct and organs enclosing the petals) which con­ separate. sists of the five fused sepals in the form of an irregular cup, is hairy, except in York road poison. The two sepals which lie behind the large showy petal (the standard) are united nearly to the apex and are longer than the other three sepals, which are united to a lesser degree.

9. The ovary (immature pod, seen in the flower) is silky-hairy, hairy or almost woolly. It is never devoid of hairs, although the pod may become hairless at maturity. The number of ovules (immature seeds) in the ovary is two in the case of the toxic species of Gastrolobium and from 6. Below the calyx, the bracts nearly four to eight in the case of the toxic always fall before the flower has fully species of Oxylobium. The number of expanded. Bracts are small, leaf-like, ovules in the ovary is the sole character thin and chaffy organs, which may be seen that separates the two genera. when the flower is in bud. The number of seeds actually seen in pod may be fewer than there are ovules in the ovary.

. 0

7. The corolla (the petals) of the pea- flowered type is usually clear yellow or suffused with red, and in some species, red in colour.

Recognition and identification Some of the characteristics one should look for when seeking to differentiate toxic species of the genera Gastrolobium and Oxylobium from non-toxic species, are: 1. LEAVES: Leaves are entire, that is, they are not compound and do not consists of a number of leaflets, as in vetch, cassia,

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Journal of Agriculture, Vol 8 No 2 1967 lupin, etc. The arrangment of the leaves South-Western distribution on the stem is strictly opposite or in The distribution of the toxic species of whorls of three, four or more, arising from the genera Gastrolobium and Oxylobium the same level. They are not alternate in the districts of the South-Western or irregularly arranged. (Some exceptions Vegetation Province is as follows: exist where certain forms of toxic species may have leaves that are irregularly BOX POISON: Irwin, Avon, Darling, arranged). Several non-toxic plants also Stirling and Eyre. possess leaves that are arranged opposite PRICKLY POISON: Irwin, Avon, Darl­ to each other. ing, Warren and Stirling. YORK ROAD POISON: Irwin, Avon, 2. STIPULES: Stipules are present; Darling and Stirling. one on either side of the leaf-stalk or base HEART-LEAF POISON: Darling, War­ of the leaf. These can fall early, par­ ren, Stirling and Eyre. ticularly in rock poison, so that when GILBERNINE POISON: Irwin, Avon looking for them, young branches should and Stirling. be closely examined. Stipules may also be SANDPLAIN POISON: Irwin, Avon present on non-toxic plants, including and Stirling. those possessing leaves that are arranged CLUSTER POISON: Irwin, Avon and in opposites. Stirling. RUNNER POISON: Avon, Darling and 3. FLOWERS: Flowers are yellow, yellow Stirling. suffused with red, or occasionally red. BULLOCH POISON: Avon, Darling They are never blue or violet. and Stirling. THICK-LEAF POISON: Avon Warren 4. INFLORESCENCES: The inflore­ and Stirling. scences are many-flowered racemes which are terminal on the branches or arise from WODJIL POISON: Irwin and Avon. the upper leaf axils. They are never in ROCK POISON: Irwin and Avon. clusters along the branches, in the axils CHAMPION BAY POISON: Irwin and of the stem leaves. Darling. HORNED POISON: Irwin and Darling. Certain ncn-toxic species closely NARROW-LEAF POISON: Avon and resemble poison plants and appear to Eyre. possess all the characters required to CRINKLE-LEAF POISON: Darling and identify poison plants. Close inspection Warren. of these will reveal leaves that are WOOLLY POISON: Darling and Stirl­ irregularly (not strictly) whorled, stipules ing. that are absent, inflorescences that are STIRLING RANGE POISON: Stirling not racemes, or flowers that are of a and Eyre. different colour. HUTT RIVER POISON: Irwin. SCALE-LEAF POISON: Irwin. Distribution BERRY POISON: Avon. The toxic species of the genera Gastro- ROE'S POISON: Avon. lobium and Oxylobium are for the most HOOK-POINT POISON: Avon. Part restricted to the South-Western SPIKE POISON: Avon. Vegetation Province of Western Australia. RIVER POISON: Warren. The exceptions to this are wallflower MALLET POISON: Stirling. Poison found in the Northern Province, in SLENDER POISON: Eyre. Hann and Fortescue districts, and extend­ BROTHER-BROTHER: Eyre. ing into the Northern Territory and across to Queensland; kite-leaf poison or Breelya, NET-LEAF POISON: Eyre. found in the Eremaean Vegetation Pro­ MT. RAGGED POISON: Eyre. vince, in the Austin district; and granite OXYLOBIUM RIGIDUM: Eyre. Poison, box poison, prickly poison and Species with the widest range of distri­ Wodjil poison, also found in the Eremaean bution, such as box poison and prickly Province, in the Coolgardie district. poison, display considerable variation in 47

Journal of Agriculture, Vol 8 No 2 1967 1'5 117 119 121 123 125 127 1 1 1 F WESTERN AUSTRALIA —DISTRICTS IN WHICH TOXIC PLANTS ARE FOUND (see Text for Distribution Details)

113 115 117 119 121 123 125 127 129 43

Journal of Agriculture, Vol 8 No 2 1967 form. Species with very localised distri­ bution, such as scale-leaf poison and spike

poison, show little or no variation in form. PALLID ZONE

Ecology TRANSITIONAL ZONE

Most of the South-Western Vegetation PARENT ROCK Province occupies the "old plateau" or peneplain, which due to subsequent dis­ section, has given rise to the present- Along watercourses, on alluvial soils, day landscape of high ironstone-capped particularly in the lower South-West, may "hills," often bounded by "breakaways," be found heart-leaf poison, slender poison, sloping down in gentle terraces to the and river poison. more recent river valley systems. The tops of the "hills" consist of iron­ Toxicity stone material which may be overlain Stock losses attributable to the toxic with sand. Down the valley slopes the species of the genera Gastrolobium and soils consist of sand or gravel or both, Oxylobium, were experienced in the very overlying a heavier subsoil. The lower earliest days of settlement in Western terraces of the valley floor consist of the Australia. In 1837 mortalities in sheep better class red or brown soils of the and goats were recorded at Guildford, on agricultural region. land where "similar losses (were suffered) The main vegetation forms of this some years back," and in which "the region consist of the karri and jarrah animals were attacked with staggering fits forests; the tuart, wandoo, york gum and and were found dead shortly afterwards." salmon gum woodlands; the mallee, Suspicion was first thrown on a mem­ wodjil and tamar scrub; and the sand- ber of the genus Gastrolobium when it Plain vegetation. was observed that on the occasions that On rocky outcrops where the parent animals ate a certain leguminous plant, rock (granite, quartzite or sandstone) is they were affected, whereas when they exposed, it is not unusual to find toxic avoided it no losses were sustained. Feed­ species like heart-leaf poison, rock poison, ing trials conducted as early as 1839 D°x poison, granite poison, Roe's poison, showed that the observed leguminous kite-leaf poison, brother-brother, net-leaf plant, almost certainly York road poison, Poison, Oxylobium rigidum, York road was toxic to stock. Poison, gilbernine poison, hook-point Today, as a result of intensive investi­ Poison, horned poison, Stirling Range gations undertaken over the years into Poison, Mount Ragged poison, narrow-leaf the toxicity of these plants, the number Poison and prickly poison. of poison plants of this group stands at 34. On gravelly or white or mottled clay The characterisation or identification of soils of the pallid zone, just below the the toxic principle of a poison plant is a -ronstone ridges or hills, may be seen necessary prerequisite to other studies on species such as wodjil poison, Champion poison plants. The first unsuccessful Bay poison, Hutt river poison, prickly attempt to isolate the toxic principle in Poison, York road poison, bullock poison, toxic members of the genera Gastrolobium sandplain poison, narrow-leaf poison. and Oxylobium was made in 1896. It was berry poison, spike poison, cluster poison, not until 1964 that the toxic substance box poison, thick-leaf poison, runner mono-fluoroacetic acid was eventually Poison and woolly poison. isolated, independently and almost simul­ On the ironstone soils particularly taneously, from the Northern Australian near the edge of "breakaways," or on the wallflower poison and from box poison and cops of granite tors bearing remnants of rock poison of south-western Australia. ^on-stone "capping," may be seen sand- On the basis of the botanical relation­ Plain poison York road poison, prickly ship of poison plants, and the charac­ Poison, rock poison and crinkle-leaf teristic poisoning syndrome displayed by Poison. affected stock, there can be little doubt

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Journal of Agriculture, Vol 8 No 2 1967 that the main toxic radical for all mem­ Cluster poison has contained 1,300, 800 and bers of the group is mono-fluoroacetic 600 parts per million of the toxic radical acid. while thick-leaf poison has contained This substance, which has been isolated 1,350, 150 and 100 parts per million of the from the South African gifblaar (Dicha- toxic radical. petalum cymosum) and other Dictiapeta- Even within an area of one square lum species and from the gigyea chain, variable results have been obtained, (Acacia georginae) of Queensland and the with levels of sodium fluoro-acetate rang­ Northern Territory, is better known as its ing from 1,000 to 2,500 parts per million sodium salt "1080", the poison widely used in Box poison and from 100 to 1,000 parts in rabbit control. per million in Rock poison. The toxic radical which may be present in poison plants at all times of the year, and so provide a constant hazard to stock, rises dramatically at the flowering HOW TO PREPARE PLANT and pod stage, and when the plant is SPECIMENS FOR IDENTIFICATION making rapid growth. The sudden and plentiful supply of soil moisture after 1. Collect and consecutively num­ summer thunderstorms brings about a ber duplicate sets of specimens. One rapid increase in toxicity. set should be submitted for identifica­ Much lower quantities of plant material tion and the other set retained as a are required during these "flush" periods, reference collection to check with to provide lethal doses to stock. identifications. Chemical analyses conducted by the Government Chemical Laboratories have 2. Select representative plant shown that plants like net-leaf poison, material; avoid atypical, damaged or thickleaf poison, cluster poison, river malformed material. Poison, box poison and rock poison, may contain over 1,000 parts per million of the 3. Select specimens that are as toxic radical in terms of sodium fluoro- complete as possible—with stem, acetate on an air dry basis. At this level leaves and flowers (and fruit if poss­ of toxicity 0.88 ounces of plant material is ible). sufficient to kill a 110 lb sheep. 4. Prepare notes on the plant, its One sample of box poison recently associated pJant cover, soil type, topo­ analysed contained 2,500 parts per million graphy, location number, etc. °f sodium fluoro-acetate. Brother-brother and kite-leaf poison 5. Press and dry plant specimens may each contain over 500 parts per million between sheets of newspaper under of sodium fluoro-acetate, while plants with pressure. Change papers to increase over 100 parts per million of the toxic radi­ rate of drying and to prevent develop­ cal include wodjil poison, York road poison, ment of mould growth on specimens. Roe's poison, prickly poison, berry poison, 6. Keep your duplicate set (in Stirling Range poison, spike poison, gilber- newspaper folders) in a dry place. nine poison, heart-leaf poison, hookpoint Naphthalene flakes sprinkled over the Poison, sandplain poison, Champion Bay specimens should keep them free of Poison and woolly poison. insect attack. The toxic radical has not so far been de­ tected chemically (less than 30 parts per 7. Prepare specimens for mailing million) in runner poison, horned poison, by placing individual specimens be­ bullock poison, Mt. Ragged poison, crinkle- tween sheets of newspaper placed in a teaf poison, slender poison and Oxylobium cardboard container or between stiff rigidum. sheets of cardboard. Wrap container Variable results have been obtained with or cardboard covers firmly in brown several species. For example, box poison paper and string, and address and mail collected from different localities has con­ the parcel with an accompanying letter tained 2,500, 1,220, 550, 120 and 100 parts to the Department of Agriculture. Per million of sodium fluoro-acetate. 51

Journal of Agriculture, Vol 8 No 2 1967 These variations are due to several grubbed bushes should be burnt rather factors, not the least of which is varietal than left for stock to consume. differences within the species. For ex­ There is no effective practical antidote ample, in prickly poison the variety for stock poisoned by members of the grandiflorum is more toxic than other genera Gastrolobium and Oxylobium. varieties. Variation in toxicity may depend upon CONCLUSIONS AND the metabolic activity of the plant. Plants showing active growth are generally more RECOMMENDATIONS toxic than less actively-growing plants. The toxic members of the genera Gas­ The available fluorine in the soil and the trolobium and Oxylobium are highly acidity or alkalinity of the soil also affects dangerous poison plants, by virtue of toxicity, since uptake of fluorine by plants • their extreme toxic nature, for and its conversion to nono-fluoro-acetic which no antidote is available, acid depends on the amount of fluorine available, while fluorine uptake is en­ • their apparent palatability to hanced by greater acidity in the soil. stock, Cattle, sheep, goats, pigs, horses, as well • their wide distribution in the as cats and dogs, are highly susceptible main stock-raising areas of West­ to the toxic radical, whereas certain ern Australia. marsupials and birds are less susceptible. Farmers are urged to These creatures eat the seeds of poison • learn to recognise the plants, plants with apparent immunity. Dogs and cats fed on the carcasses of these animals • avoid exposing stock to the have died in convulsions, through the hazards of the plants, ingestion of the toxic radical present in • eradicate all plants, before in­ their entrails. fested areas are subsequently utilised for stock-raising activi­ Box poison, heart-leaf poison, rock poison, and others which are soft leaved ties. and apparently very palatable to stock Farmers not certain of the identity of a present a very serious threat at all times. suspected poison plant should not hesi­ Prickly poison and bullock poison, which tate to submit a specimen of the plant have harsh, prickly and relatively un­ for identification to:— palatable leaves, become hazardous to The Officer in Charge, stock only with the appearance of fresh Botany Branch, young, and more palatable leaves, or when Department of Agriculture, there is a shortage of other feed. Dried Jarrah Road, leaves still remain toxic to stock so South Perth.

52

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Journal of Agriculture, Vol 8 No 2 1967