The war on weeds

With the recent rains that Melbourne has experienced, our gardens have received a much-needed boost. But it’s not only the ornamental and edible plants that have benefited from the extra moisture. The downpours, followed by relatively mild weather, have meant that many weeds have come out in force again.

Over the years, horticulturalists have developed a wide range of effective techniques for weed removal that can be used in the home garden. Beside hand-weeding, one of the most common methods is via the application of weedicide, especially glyphosate, the active ingredient in Roundup. Roundup is most certainly very effective on a wide variety of weeds, killing them within a matter of weeks, and is heavily used in the agricultural industry. However, growing research has highlighted that the use of Roundup may have drastic consequences for both humans and the environment in general. This has been highlighted by the recent cases in the U.S. where chemical giant Bayer, the owner of Roundup, has been successfully sued by people claiming that their heavy use of Roundup over many years was a factor in them acquiring non-Hodgkin’s lymphoma. The World Health Organisation had already listed glyphosate as a probable carcinogen. But it’s not only humans that are affected by glyphosate. A recent study in honey bees, for example, revealed that certain species of bacteria found in the gut of bees decreased in abundance when bees were exposed to glyphosate. Gut bacteria are crucial in helping regulate immune systems and the glyphosate-exposed bees did indeed have reduced immune function. This led to these bees being less likely to survive when exposed to a pathogen known to infect bees. Could this be contributing to the global demise in bee populations?

Thankfully, there are many other options for weed control that are less harmful to ourselves and the environment. Some store-bought herbicides, such as Slasher Weedkiller, are certified Organic products and therefore do less harm to the environment. Or why not try making your own weedicide? Pouring boiling water over smaller weeds in paving works wonders, while a mix of vinegar, salt and soap is also effective. The salt shrivels up the leaves, while the vinegar burns the leaves. However, this vinegar mix works best on younger weeds or annuals (as opposed to perennials) and heavy use of this spray in garden beds can increase soil-salt levels and acidity, both of which are not great for plant growth.

If you have a garden bed with many weeds and few plants (e.g., an unused veggie plot), solarising can be effective. This technique involves covering the soil with a sheet of plastic for 4-6 weeks, preferably over the warmer months. During this period, soil temperatures can rise over 50 degrees Celsius, which can effectively kill weeds, weed seeds and pathogens within the soil (although beneficial soil bacteria would also be killed during this process). In addition, some research has found that solarisation also increases the availability of nutrients into the soil, which would aid in plant growth.

For large-scale weed control, an increasingly popular method is weed steaming, whereby heated water and steam are applied to weeds. The steam destroys plant cells and therefore effectively kills the plant. Given that it only uses water, this method is a great method in sensitive areas, such as around schools. Indeed, the city of Maroondah, for example, has already conducted trials of steam-weeding in, for example, playground areas in recreational reserves.

Finally, as the saying goes, prevention is better than the cure. A great way to stop weeds popping up in your garden in the first place is by adding either a thick layer of mulch or a growing a groundcover. Mulches block out the sunlight, which may prevent weed seeds from germinating, while groundcovers outcompete weeds for growing space. Many great native groundcovers that will grow well in the Melbourne area exist, including pigface (Carpobrotus), many species of grevilleas, yellow buttons (Chrysocephalum) or the native daisy (Brachyscome). Kidney weed (Dichondra repens) is a native ground cover which is good for shady areas. It spreads fast and can also be used as a lawn substitute. Mulches and groundcovers also have the added benefit of preventing water loss, keeping soil temperatures constant and adding nutrients to the soil.

So, when you’re next ready to battle those weeds that seem to be fighting to take over your garden, resist the temptation of reaching for the glyphosate. Although it is certainly extremely effective in killing weeds, does this really justify its use, when the detrimental impacts of glyphosate on our health and environment are becoming increasingly clear? Why not instead try a more ecofriendly approach in winning the battle against weeds? And if all else fails, pulling out weeds by the hand doubles as a great workout.