Rat Proofing My Gardening

By

Maclaine Oskin

Intern with Sustainable House

Maclaine here!

I’m an intern at Sustainable House with Michael Mobbs where I’ve been working for about 4 weeks now and am just about halfway through my study abroad program in Sydney.

I’m originally from the US where I study Environmental Science and Urban Planning at the University of Pittsburgh in Pennsylvania.

A week or so ago while toiling away doing back-breaking work on the streets of Chippendale I had the honour of beholding a most majestic and auspicious sight; the wormtailed butt of a rat! As it scurried away and disappeared into the ether of the city as abruptly as it had materialized in all of my awe (read: alarm) and excitement (read: horror), I exclaimed loudly, “Eewww!”. Now this might seem a little unfair to the rat, but in my defence, this was my first rat sighting ever. Growing up in the suburbs in Pennsylvania my childhood was ratless. I thought I might have a chance at a rat encounter when I went away for college in the City of Pittsburgh, alas I only ever heard rumors from other students of rats rifling through the garbage cans in South Oakland though I was never so lucky to see one in person.

Rats.

You may have your own stories of sightings and encounters, or you may recognize them most famously associated with the French dish ratatouille, the bubonic plague, or the New York subway. However, rats are also common amongst the city streets and as pests in gardens and compost bins scavenging for readily available food sources like growing vegetables in a backyard garden plot or food scraps in a compost bin.

Though cities are mainly viewed as human spaces, each city has a vibrant ecosystem of wildlife that calls the city home. For example, in Sydney, Australia beyond the most commonly associated city critters like rats or cockroaches it hosts a multitude of wildlife such as foxes, bats, bandicoots, possums, a variety of bird life, as well as those on the fringes of the city may get visits from friends like wallabies and kangaroos. It is important for me during my internship to understand the variety of life that flourishes in a city and how to manage the compost options in the streets of Chippendale where I’mm interning to prevent unwanted visitors such as the rat.

Michael told me last week he was talking to two big burly men loading the street’s weekly garbage bins into a garbage truck when one man gave a loud shriek as he was loading a garbage bin and the three of them looked on in amazement as a rat lept high into the air out of that bin. Michael said to the shrieking man, “How did the rat get into the bin? Is that the first time that’s happened?”, and the man replied, “No, it happens lots. They’re amazing where they can get into.”

Some may wonder what the humble rat has done to earn an infamously poor reputation amongst the populace and why they are considered such a pest.

The answer is that rats are often associated with unsanitary conditions given the contamination of resources via rat droppings and their historic link as transmitters and carriers of diseases as well as other pests such as fleas or ticks within their fur. They can carry or transmit diseases such as leptospirosis, rat bite fever, Lymes disease, and more through bites, contaminated materials, or contact. Rats by gnawing on wood or wire can also damage property and house infrastructure overall contributing to their profile as a bad neighbour. So how do we prevent rats from moving in?

Compost bins in particular can be extremely attractive places for rats with a plentiful food supply and nesting material combined with a protected warm enclosed space. The first means of guarding your compost against pests is ensuring that the compost bin is tightly secured and closed and that there are no gaps or holes rats and other pests can squeeze into. For open-bottomed bins or to be extra cautious, adding metal wiring that rats can’t chew through can help prevent sneaky intruders from attempting to pinch a meal. For further rat prevention, consistent good compost habits such as consistently turning the bins is important.

Rats like secure places and don’t like to be disturbed by loud noises, so consistently turning your compost disrupts any nesting attempts, and placing compost bins in high-traffic areas can discourage rat nesting and activity near your compost bin. Furthermore, rats prefer dry spaces to nest, so keeping your compost moist or watering regularly as needed can be an effective way to dissuade rat infestations. Make sure there are not any isolated pockets of food scraps or undecomposed patches that can be alluring to rats. Consistently turning our compost and prioritizing composting of quickly breaking down food scraps such as vegetables and fruits instead of cooked foods or bread that take a long time to break down can be better alternatives. Overall, keeping a clean space and getting rid of any open food or water sources rats can take advantage of will go a long way.

Once a rat infestation has taken hold, rodent traps are an option including lethal, live, and baited traps to rid a household of unwanted furry friends.

However, the easiest way to deal with a problem like this in the first place is prevention. One such way to prevent rats beyond the suggestions for good anti-rat garden and compost management is the strategic use of rat-deterring herbs and plants. Growing plants that are regarded to deter rats such as mint, onion, sage, marigolds, lavender, and catnip around compost bins or dispersed throughout a garden can help to keep the rats at bay.

Let’s take a deeper look into the true impact of mint as a rat deterrent as an example. Mint plant stems from the genus Mentha and is a well-known aromatic perennial herb that is popularly grown in gardens, used in food, and essential oils for its attractive odor, taste, and medicinal properties. It comes in a multitude of varieties with over 13 species of mint plants including peppermint (Mentha piperita), spearmint (Mentha spicata), and horse mint (Mentha longifolia). The potency and composition of the chemicals in mint responsible for its distinctive properties and strong odor such as menthol vary considerably based upon environment, climate, and life stage of the mint plant.

There are anecdotal claims and observations that mint is an effective rodent deterrent as a result of its strong odor from home garden blogs and articles. However, actual scientific research and literature on the topic of mint as a rat repellent is sparse and needs further development of the topic to come to a conclusive resolution in terms of efficacy as a deterrent much less to provide a viable comparison of efficacy between species of mint plants. Although, spearmint in a profile on the efficacy of mint and mint oil as a deterrent from Cornell University found there to be a limited oral toxicity (direct consumption of mint by rats is slightly toxic) of mint in rats with evidence of mint consumption leading to liver damage. Additionally, this study has found that mint has a generalized negative impact on the fertility of male rats diminishing productivity (Baker 2018). More academic research is needed on the topic to fully ascertain the link between mint and effective use as a pesticide.

As a result, here at Sustainable House we decided to trial this method and plant common Peppermint in coolseats on the streets of Chippendale to see if this affects behaviour.

Though the Coolseats are rat proof with metal wiring protecting the compost bins, there are still rats throughout the city streets that we want to keep away from visiting and eating the growing plants in the garden beds. One or two have tried to dig near the metal wiring unsuccessfully as seen in Figure 4, where the soil is seen to be disturbed and leave litter has begun to fill in the hole.

My fellow interns and I planted five peppermint plants (Mentha piperita) at the sides of a few Coolseat benches as an extra layer of prevention and deterrent from unwanted visitors from investigating the compost or edible plants as seen above.

As a result of the week or so since planting the mint, we have not seen any new visitors or evidence of visitation, no new holes have been dug or droppings left.

I will continue to monitor the garden beds for evidence of pests and update the blog throughout my internship to see whether the mint plants prove to be an effective ward against rodents

 What I’m doing with my food waste

As an intern at Sustainable House, we have the option to compost some of our food waste in the Chippendale neighbourhood where we work.

This is very different from how I managed my food waste at my home university, in which, after my meals, I generally did not really consider my impact on food waste. In college I was on a meal plan and mainly ate at dining halls or out at restaurants, where each place had their own food waste policy and disposal systems.

For me personally, this has taken a shift in habits which are always hard to develop when you already have such an entrenched routine. I personally don’t feel like I have been very consistent in this process and feel like I have to regularly remind myself not to throw away my food scraps and what can and can not go in the compost bin. I also think one of the things that I struggle with is the motivation to compost since the drop-off site in Chippendale is so far away, I think if I had a backyard garden with my own composter or a closer drop-off location, I would be more excited.

Though sometimes it feels inconvenient, I can see the impact it is making through the Coolseats Calculator that estimates the amount of carbon emissions reduced by my composting efforts, as seen above which has helped drive my motivation to continue to improve my habits and commit to the process. The calculator is free to download and I’m finding it interesting to use.

Maybe by composting I’ll make it harder for rats to find something to eat.

References:

–       “Mammals in Sydney: Get Involved.” Environment and Heritage, www.environment.nsw.gov.au/get-involved/sydney-nature/wildlife/mammals-in-sydney#:~:text=Even highly developed areas of, alongside us in urban areas. Accessed 26 Feb. 2025.

–       Coleby-Williams, Jerry. “You Dirty Rat.” Gardening Australia, Gardening Australia, 27 Mar. 2020, www.abc.net.au/gardening/how-to/you-dirty-rat/12095852.

–       “Rats in the Garden.” BBC Gardeners World Magazine, BBC Gardeners World Magazine, 1 Feb. 2025, www.gardenersworld.com/plants/rats-in-the-garden/.

–       “Get Rid of Rats in Your Garden without Poison or Traps.” Better Homes and Gardens, 12 July 2024, www.bhg.com.au/garden/gardening/how-to-get-rid-of-rats-in-your-garden/.

–       EPA, Environmental Protection Agency, www.epa.gov/rodenticides/options-dealing-rodent-infestations. Accessed 25 Feb. 2025.

–       Baker, Brian P, and Jennifer A Grant. “Mint and Mint Oil Profile.” Cornell Cooperative Extension: Integrated Pest Management New York State, 2018, ecommons.cornell.edu/items/b0afb3af-9547-451a-a1e9-51327e3de347.

–       “Controlling Wild Rodent Infestations.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, www.cdc.gov/healthy-pets/rodent-control/index.html. Accessed 26 Feb. 2025.