A novel way to stop animals eating your plants

It is possible to shield plants by fooling would-be grazers with the smell of a plant they typically avoid. It’s a low cost, humane strategy that has plenty of potential. Find out how to do it.

There’s help at hand for discouraging some herbivorous mammals.

How to protect plants and food crops from animals such as possums, birds, rabbits, rats, bandicoots, deer and wallabies? There’s help at hand for discouraging some herbivorous mammals in a recent study from University of Sydney researchers. Their findings, published in Nature Ecology and Evolution, showed it’s possible to shield plants by fooling the would-be grazers with the smell of a plant they typically avoid. It’s a low cost, humane strategy that has plenty of potential. The experiment used swamp wallabies as the model herbivore, and tree seedlings of Eucalyptus punctata as the food source. The unpalatable shrub selected was Boronia pinnata, a plant with pungent foliage from numerous oil glands in the leaves, whose odour the researchers chemically replicated. Both this artificial odour and the real plants were equally successful in deterring wallaby browsing; plants in the untreated controls were 17-20 times more likely to be eaten.

The study’s lead author, Patrick Finnerty, says “Given that many herbivores use plant odour as their primary sense to forage, this method provides a new approach that could be used to help protect valued plants globally, either in conservation work or in protecting agricultural and forestry crops.”

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Quick and Tasty

There are plenty of cool season crops to plant now. The four below grow to harvestable size quickly and are highly productive in small spaces.

English spinach.

Sprouting broccoli

Others include spring onions, carrots, kale and Asian greens such as pak choi and mizuna.

Climbing snow pea.

Lettuce.

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Q&A

My efforts to eradicate onion weed – hand digging, different weedkillers – have so far been unsuccessful. Is there an alternative to fine sieving the soil?

John Laing, Central Coast, NSW

Digging dislodges the many tiny bulblets around the mother bulb, making the problem worse. Glyphosate (Roundup, Zero) works best when plants are at flowering stage. Paint on or use wipe-on gel if close to other plants. Always snap off flowers before seeds form. Most effective is suppression – lay newspaper, six to eight sheets thick, around plants, and overlap so there are no gaps. Wet it as you go to stop it blowing around, then cover with mulch.

My privacy hedge of Mexican cypress (Cupressus lusitanica) is about 1.5m tall. How do I prune them now in order to maintain them at 2.5m tall?

Heather Hinrichsen, Mornington Peninsula, Vic

This large, fast-growing species can reach 20m or more. A smaller, 10m variety named “Private Green” is denser and slower. Conifers differ from many hedging plants in that they don’t reshoot from cuts into old wood. You need to prune only young, whippy growth. All hedges should be pruned little and often from the outset to develop into dense, bushy screens.

A lot of the middle branches of my 8m-tall golden robinia have died off in the past two years. Why? The rest seems fine.

June McBeth, by email

Possums love this tree, eating all the foliage they can reach, often killing whole branches. Otherwise it could be borers. Look for telltale holes or the webbed sawdust called frass; poke a wire down holes to pierce the grubs inside. Borers only successfully attack trees that are already stressed (from old age, drought or root damage) so improve tree health through watering and mulching.

Send your questions to [e-mail]. The best question for May wins $120 worth of lifelike fruit and vegetable candles, handmade in Australia, from Nonnas Grocer. See the range at nonnasgrocer.com

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