The Swan River Colony’s Poison Plant Saga

Main Club meeting 4th June 2021

Our speaker was Dr Neville Marchant. Neville worked at the WA Herbarium from the age of 15 as assistant to Government Botanist, Charles Gardner, before graduating from UWA and then gaining his PhD in Plant Taxonomy at Cambridge. After that, he worked at the WA Herbarium again, and later became its director. He was involved in the development of FloraBase, was a co-author of The Flora of the Perth Region, and has been given a Member of the Order of Australia award (AM) for his botanical contributions.

Neville told us the story of how the early settlers in the Swan River Colony were confused over the causes of mysterious stock losses that occurred frequently from 1829. At first, all kinds of reasons for the stock deaths were proposed, such as overeating on lush pastures, bad weather, bad air, water on the brain, or that the stock had been driven too hard. The story involves the role of two botanists in the colony – James Drummond and the German visitor Ludwig Preiss. It also involves understanding the diversity of legumes (Fabaceae) in the south west corner of WA.

The south west of WA is unique in its diversity of shrubby legumes, including toxic pea-flowered ones, as well for its Christmas Tree, its Kingia, and its huge diversity of Sundews (Drosera). It has around 1500 species in the family Myrtaceae, again mostly shrubby species. Plants have developed a huge diversity of flower structures, evolving in response to varied pollination systems. Many shrubs from a range of families have prickly defences against grazing, some have anti-feedant chemicals, some being highly toxic. “Eggs and bacon” coloured flowers of legumes have evolved to be effective attractants to pollinators so that many species of different genera may share the same pollinator. About one-third of the “eggs and bacon’ flowered Gastrolobium species may contain the toxin fluoroacetate. Native marsupials have developed immunity to this poison; the manufactured version of fluoroacetate, 1080, is effective for feral animal control.

James Drummond arrived on the Parmelia in 1829, along with James Stirling and John Septimus Roe. Eventually he took up land at Toodyay. He was an experienced botanist and developed a sound reputation for giving advice to farmers. He had developed a good knowledge of the local flora, using books like Robert Brown’s 1810 Prodromus, which presented descriptions of plants collected while on Flinders’ 1801-1803 expedition around Australia. But despite his good qualities, and being a prolific plant collector, Neville says that Drummond was a sloppy collector, not labelling his collections with information on such things as location, making it difficult to locate where Drummond’s specimens had been gathered. Even though Heart-leaf poison (Gastrolobium bilobum), had been formally described in 1811, Drummond could not name this plant when he found it around the south coast. Ludwig Preiss, on the other hand, was a careful and systematic collector, and had also collected Heart-leaf poison as well as several other poison peas.

By 1840, stock losses were causing serious concern, especially on the Albany and the York roads, and there was even adverse publicity about these in the Sydney Herald. Drummond believed that a toxic plant was responsible for stock deaths. He first blamed what we now know as Woodbridge poison (Isotoma hypocrateriformis), because it looked like a toxic European plant. Preiss disputed this, and there was much ill-feeling.

Eventually, tests were done near Kojonup and Williams by feeding animals with suspected plants. Isotoma had no effect. York Road poison or “sage plant” (Gastrolobium calycinum) killed a sheep; however, this was initially regarded as being due to another cause. A further rift developed between Drummond and Preiss. Preiss was supported by his lawyer friend, William Nairn Clark, who belittled Drummond. Clark was, politely, said to have a restless temperament; other descriptions were rife. Preiss wanted farmers to cultivate all legumes as nutritious fodder, and he drank a glass of supposedly “sage plant” juice (and survived) to prove that it was not responsible, ignoring the fact that some animals had died after eating it in the test. But in 1841 it was at last proven that some pea-flowered plants in the genus Gastrolobium, including the “sage plant” do in fact kill sheep and goats, and a dog died at a Guildford feeding trial within hours of eating the meat. The reason for mixed results and the long period of uncertainty and confusion for settlers was probably that the poison peas are only toxic when budding, flowering or producing seed, and in early growth of new shoots.

Neville concluded by saying “Thank heavens for the poison plants”, because they have been a reason for conservation of some areas such as the fantastic Stirling Range. On the other hand, poison plants have been so widely eradicated that some species have become endangered. So, the poison plant saga is a long and convoluted one.

Mike Gregson