When humans talk of “repellent”, it brings to mind something nasty. But, in the garden, the sweetest perfumes can act as pest repellents — not because the garden pests necessarily dislike them, but because they disguise the scent of garden pests’ food supply.
Want to keep cabbage white butterflies from your cabbages? Stink bugs from the lime trees? Aphids from the roses? Consider some of the plants below. Use them lavishly. As a rule, you need 10 “repellents” to disguise each plant you are trying to protect, but this can vary. Use your own nose as a guide. If you can smell sweet peas instead of cabbages as you pass the vegies, chances are your garden is truly repellent — as well as gorgeous, productive and wonderfully pest-free.
Basil
Basil is possibly the best repellent or “disguising” scent I know. It’s easily grown, can be perennial in frost-free areas and is strongly scented, with a smell unlike the other plants you will be trying to protect.
A few stunted plants, however, will be of little or no use to your plants or your kitchen. You need great, lush, knee-high groves of basil to really work. Try massed purple-leafed basil under your rose bushes, among the cabbages or between the tomatoes to — possibly — repel fruit fly and helianthus caterpillars. Although, the scent of ripe tomatoes is stronger than basil, so you’ll need to pick your tomatoes as soon as they are coloured for this to work. Never, ever let overripe tomatoes fall to the ground and lie there rotting. It’s like putting up a flashing neon sign: fruit fly welcome here!
Anise hyssop (Agastache spp)
Anise hyssop is truly stunning in the garden, especially grown en masse. This strongly anise-scented perennial grows to about a metre high, is easily hedged, drought-hardy and blooms superbly for at least six months of the year in most climates. It is excellent around citrus and other fruit trees to ward off pests.
Coriander (Coriandrum sativum)
Coriander has a reputation for repelling aphids and other sap suckers, but for it to be effective plants need to be surrounded by the coriander. It’s also most effective when flowering. Sadly, coriander flowers and goes to seed all too readily — any hiccup in its growing season may send it to seed. It grows best at our place in dappled light under fruit trees towards the end of summer and into autumn, rather than sown in spring. It’s too temperamental here to be really useful, but if you’ve found the secret to growing it large, lovely and long-lasting, use it as a pest repellent, too.
Sweet peas
These have to be the climbing old-fashioned sweet peas with the strong, glorious, old-fashioned scent. The pest-repellent effect is only when they are blooming, and only if you have LOTS. Try them on trellises around your veg garden to repel butterflies and moths that may lay caterpillar eggs, and other flying pests. Our vegie garden is surrounded by high builders’ mesh, which not only keeps out wallabies and wombats but also provides a 2m-high trellis for climbing beans and sweet peas. The scent is incredible … as long as the wallabies haven’t found them and poked their paws in to eat them all.
Salvias
There are hundreds of perennial salvia cultivars and varieties in Australia. Most have strongly scented leaves and, if you choose the correct ones for your climate, are stunningly hardy, drought-resistant and beautiful plants, ranging from ground covers to large clumps or hedges over 2m tall. Check the label before you buy — some are not frost tolerant. All will accept dappled sunlight, though they grow best in full sun.
I find tall-growing salvias excellent companions for fruit trees and roses, especially when they twine among the branches. There have been no pests whatsoever on any of my fruit trees or roses grown among the many salvias I have trialled here, even when others less than 2m away have been covered with stink bugs or citrus scale. The salvias only minimally compete for nutrients and water, and are long blooming. They also are superb bird attractors (and the birds will then eat pests, too, especially in breeding season for their young) and will attract hoverflies and other predators.
Try fruit salad sage, a frost-sensitive salvia with richly scented leaves and stunning red flowers through winter and spring. Use it to flavour fruit salads or add young tender leaves to your sandwiches. Or try pineapple sage, a tall, wide sage bush with fragrant pineapple-scented leaves. It tolerates only light frost. It flowers through most of summer and into winter. Birds and insects love it (the birds also help clear the aphids and mites off our roses near the sage bushes).
Grow pineapple sage near climbing roses, under fruit trees and between fruit bushes to repel pests and attract predators. Use it to flavour cold drinks and fruit salads or use young tender leaves in sandwiches and wraps. Don’t cook with it, though; it turns bitter.
Geranium/pelargonium
Most so-called scented-leafed geraniums are of the allied genus, pelargonium. Both scented-leafed geraniums and pelargoniums will help repel pests, but only as far as the scent persists. I’ve trailed ivy-leafed scented pelargoniums under our citrus. They repel stink bugs from the lower half of the tree, but not the top — and stink bugs prefer the top with its new shoots, anyway. But an understorey can be extremely useful to help protect young trees.
I have found the most repellent pelargoniums to be the slightly sticky ivy-leafed spice-scented pelargonium and the soft downy-leafed peppermint pelargonium. The stronger the scent, the more effective they are, so sniff before you buy.
In fact, just keep sniffing. Whenever you find a strong plant scent that you adore, whether the perfume comes from the leaves or flowers, consider whether, or how, you can use it in the garden. You’ll be getting a “toofer”, or “two for one”: a stunning scent for yourself and all who pass through your garden, and a sneaky disguise for the plants you love.
