Retiree's Lunch Update May 2021

Written by  Dr Richard Thwaites, FRACI CChem

Published 7 June 2021

A CHEMIST LOOKS AT WEEDS

The question on everybody’s lips is what do Costa Georgiadis from the ABC Program “Gardening Australia” and Ian Rae from the University of Melbourne have in common?  It’s clearly not their hair styles, of course.  The right answer is their immense knowledge of plants.  In Ian’s case, as he demonstrated at the recent Retirees’ virtual lunch held via Zoom on May 4th, he is a real expert on weeds.

When people leave work, either when they retire or are made redundant, they are often told to go on “gardening leave”.   So, our audience of retirees for Ian’s talk included many beneficiaries of “gardening leave”.  

In fact, Ian gave a magnificent “Tour de force” (or perhaps more accurately, a “Tour de the Western Suburbs”) as he explained nearly everything there is to know about weeds.
Ian pointed out that weeds occur not only in our gardens, but also along disused railway lines and footpaths, on wasteland, and around abandoned factories.  They also occur on Council property, in parks, botanic gardens and around Municipal buildings.  Ian showed numerous superb photos of weeds, taken mainly in Melbourne’s western suburbs, and told his audience where he had found them and a bit about their history, the chemical composition of leaves, stalks and stems, and other background information.

Carl Linnaeus is widely regarded as the author and founder of Taxonomy, the science of identifying, naming and classifying various types of organism, especially plants.  So all the weeds mentioned by Ian had a proper scientific name as well as a more popular name, and Ian was able to tell us both and a bit of history to illustrate.  Some of the common names for weeds in Ian’s pictures are rather cute:  who can tell what Aaron’s rod, or Turnip weed or Soursob look like?   Or Artichoke Thistle, or Flax-leaf Fleabane or Morning Glory?  

What we perhaps were not aware of is how many physicians and surgeons in the 18th and 19th centuries had an interest in weeds, and often other plants, too.  Members of the medical profession had a particular interest in many types of plant because of their alleged curative properties and health benefits.  Even today, many pharmaceutical ingredients produced by sophisticated multinational companies originated from humble weeds.

During the course of his presentation, Ian showed over 30 of his photos of weeds, too many to include in this report.  A selection is included in the slides available here.  Some of the weeds Ian mentioned have local origins and appear to be indigenous to Australia.  Others were brought here (usually inadvertently) by early settlers often from Europe.  It is perhaps unfortunate that many of the imported weeds flourished in the local climate.

As chemists, we are often asked two questions.  Firstly, what chemicals are present (and are they toxic – surely not if they are “organic” and “natural” – but often yes if various alkaloids or other organic chemicals like oxalic acid are present)?  Secondly, what chemicals can we safely use to get rid of weeds?  For many who dislike using chemicals in our gardens unless we really have to (and there are many chemists who prefer not to use weedicides or other pesticides close to the house) the only option is to dig up the weeds and try and make sure if they are put on the compost heap, they don’t have lots of seeds ready to germinate when the compost is spread.   On the other hand, products like glyphosate when used sensibly are not really a significant hazard:  it’s only when people use them in an indiscriminate and uncontrolled fashion that problems can occur.

As a result of Ian’s presentation we all felt we had learned a lot more about weeds.  For the amateur gardeners among us, it’s a pity that weeds seem to grow a lot more prolifically than the vegetables, flowers and shrubs we would like to cultivate.  And maybe we learned that even in the Williamstown Botanic Gardens a little bit of France (at least in name) continues to grow prolifically – lion’s teeth (or dandelions, dent de lion, so called because of the shape of the leaves).  Dandelions are otherwise known as “pee-in-the-bed” or “pissen-lit” (from the French) because of their supposed diuretic properties.  And you can buy Dandelion and Burdock soft drink, produced in the UK since the 13th century, apparently originally invented in alcoholic form by St Thomas Aquinas, and noted for its unique flavour (a cross between aniseed and liquorice), something like Sarsaparilla, which at one stage Dr Pepper ‘s wanted to promote and commercialise. Maybe retirees who need to take diuretics for medical reasons could save a lot of money by just letting dandelions grow in their gardens and eating the plants rather than swallowing over-priced pharmaceutical pills.  Or perhaps not!

 
The next meeting of the Retirees will be held at Graduate House 12:00PM on Tuesday July 6th 2021. (Covid restrictions permitting)

Hope to see you soon!