10 Plants That Repel Caterpillars (Plants They Hate)

In a plant nursery or an ornamental garden, caterpillars can be some of the most troublesome, leaf-eating pests. Though they do have their many benefits, which include ecological diversification and their eventual metamorphosis into pollinating insects, they can ruin entire shrubs of tender plants. They rely on many economically important host species for sustenance and shelter. This makes their presence especially problematic in monoculture setups for fruits and vegetables.

Today, hundreds of species of caterpillars are known for damaging entire nurseries and farms before they can produce a substantial yield. This is why some farmers opt to use chemical-based insecticides to control their spread. Organic farmers, however, can’t afford to use toxic sprays to maintain the quality of their leafy plants. Responsible gardeners likewise prefer to use ecologically friendly methods of reducing leaf damage.

Fortunately, there are several sustainable ways of keeping caterpillar populations to a minimum. Of course, removing them by hand is always an option, but this is time-consuming and impractical in large gardens and farms. Some horticulturists opt to create an organic pest-repellent spray, but the effects of this would also have a limited reach. Instead, it would make more sense to grow the right companion plants!

1) Common sage (Salvia officinalis)

Just as many common flies, fleas, and grazers are deterred by fragrant herbs, caterpillars likewise learn to dislike them. Their bitter taste and intense aroma, which signify the presence of potent essential oils, tend to dissuade even the most voracious kinds of caterpillars. The common sage is just one of many flavorful herbs with a caterpillar-repellent oil.

Apart from repelling the larval forms of some winged insects, sage has a knack for throwing off adult moths. It isn’t a totally foolproof solution to caterpillar infestations, however, as some species have actually adapted to thriving on its bitter foliage. Nonetheless, using sage as a companion plant for leafy vegetables in the Brassicaceae family, such as brussels sprouts and cauliflower, should minimize the occurrence of cabbage worms, cabbage loopers, cabbage maggots, and more.

The best spots in which to plant stands of common sage are those receiving medium to full sun exposure. In well-draining, loamy substrates, particularly those with high nutrient concentrations, sage can grow quite fast. If you place a sage plant close to fertilized vegetables, resist the urge to enrich the soil around its roots.

2) Lavender (Lavandula spp.)

Lavender is, by far, one of the best economically important herbs for repelling pests. Apart from aiding in the maintenance of a pest-free garden, it can also add to its overall diversity and year-round interest. Fragrant, lavender spikes are always a welcome sight. You’ll be hard-pressed to find a gardener that doesn’t appreciate their muted tones and their attractiveness to beneficial insects.

There are dozens of species of lavender, but the most popularly grown varieties are generally effective as caterpillar repellents. These include English lavender (L. angustifolia), fringed lavender (L. dentata), and Spanish lavender (L. stoechas). The potent essential oils in these plants give off a scent that signifies the presence of potentially toxic phytochemicals. These make their leaves virtually unpalatable to most leaf-eating larvae.

To grow lavender as a caterpillar repellent, situate its stands close to crops and ornamentals that are frequently attacked by insects and pollinated by moths. Intact stands won’t kill any worms, but they should at least dissuade them from infesting the garden. For a more targeted or lethal solution, you may obtain a pure extract of lavender oil and incorporate it into a homemade, water-based repellent spray.

3) Hyssop (Hyssopus officinalis)

In the wild, hyssop occurs as a perennial subshrub in rocky areas and dry landscapes. This drought-tolerant plant is known for its aromatic, dark-green foliage and its bluish-purple spikes of summer blooms. A major component of many potpourris and botanical liquors, its edible yet slightly bitter and minty leaves are disliked by many grazers and leaf-eating insects.

Undeniably fragrant and beautiful, hyssop is definitely one plant you’ll want to cultivate if you intend to grow brassicas. These members of the cabbage family can be ravaged by caterpillars in just a few hours, so it’s crucial to surround them or plant them alongside pest-repellent companion plants. Large stands of hyssop should produce a fragrance that can mask the scent of vulnerable crops.

Apart from deterring caterpillars with their strong taste and smell, hyssop bushes can minimize the occurrence of infestations by attracting birds. Hyssop blooms attract hummingbirds, which can consume large numbers of small caterpillars and larvae-producing insects. They also attract parasitoid wasps, which produce larvae that parasitize adult caterpillars or the eggs of moths.

4) Mugwort (Artemisia vulgaris)

Known for being the “mother of all herbs” because of its seemingly endless list of uses in the pharmacological industry, mugwort is a fairly common plant throughout its native range. Its hardy shoots may even thrive as weeds in developed areas and in places with a large number of waste products in the substrate.

The complex leaves of mugwort are disliked by many leaf-eating larval insects because of their bitter taste and their sage-like scent. These indicate the presence of strong phytochemicals, particularly those with larvicidal properties. Camphor, which has long since been proven to be an excellent insecticide and pest repellent, is just one of the major compounds in mugwort essential oil.

Highly adaptable to a wide range of soil types, mugwort can grow and spread quite quickly. It would be best to restrict its roots to designated plots or containers that are strategically placed around more susceptible plants. Though it can bring a wealth of benefits to the garden, avoid leaving its stands unsupervised. Keep in mind that its presence can also inhibit the growth of certain types of plants.

5) Peppermint (Mentha x piperita)

Though we are often attracted to both the scent and taste of peppermint, many animals and insects take care to avoid this natural mint hybrid. The aroma of the leaves, which is particularly strong when they are rubbed or damaged, can mask the smell of nearby plants. This herb can thus be used as a caterpillar deterrent if it is planted close to leafy crops and ornamentals.

Peppermint essential oil contains a high concentration of menthol, pulegone, and other strongly-scented phytochemicals. These function as natural pesticides, protecting the leaves from being ravaged by grazers and various scent-sensitive insects in the wild. When cultivated in the right manner and restricted to dedicated areas, this herb can provide a host of environmental benefits to an organic garden.

To encourage your peppermint plant to emit a strong scent, aim to harvest its leaves and collect cuttings frequently. This should release fresh oils, signaling many insects to stay away. Apart from growing the plant itself, you may also incorporate its oils into a water-based spray. Target organic crops that may require extra protection from caterpillars.

6) Garden thyme (Thymus vulgaris)

Always a lovely addition to sunlit herb gardens with good drainage, garden thyme is a perennial herb with many uses. Its dense stands can function as low-growing borders or be cultivated as a flowering ground cover. As it rarely grows to more than 12 inches (30 cm) tall, it is unlikely to cast nearby herbs and crops in shade. Though it may be short-lived, it can easily be propagated to thrive in both focal and isolated parts of your yard or farm.

Now widely used as a culinary herb due to its unique scent and flavor, garden thyme attracts butterflies, yet repels their larval offspring. Its fine leaves are unpalatable to many insects and grazers because of their bitter taste. Moreover, its stems become increasingly woody over time and are rarely perceived as a source of sustenance by the most voracious caterpillars.

Apart from garden thyme, other close relatives and hybrids, including creeping thyme (T. serpyllum) and lemon thyme (T. citriodorus), can be grown to repel caterpillars. All of these are great companion plants for crops because their scent signatures can repel tomato hornworms, cabbage moths, corn earworms, and more! As a bonus, their vivid blooms should attract potential caterpillar predators through summer.

7) Oregano (Origanum vulgare)

Although dense and unkempt patches of mature oregano may attract a unique host of pests, a few wisely situated specimens should help deter many leaf-eating insects. This perennial herb is frequently grown as an ornamental or culinary herb in gardens throughout its native range. Due to its popularity as a flavoring ingredient, it is now widely naturalized throughout the northern hemisphere.

For the purpose of minimizing the occurrence of larval infestations, oregano is often utilized as a companion herb in organic vegetable patches and permaculture setups. Its fragrant and bitter leaves are considered unappealing by many leaf-eating insects. Its blooms attract several beneficial insects, including those that are likely to prey on or parasitize caterpillars.

When neatly maintained in hedgerows around more susceptible crops like broccoli, kale, brussels sprouts, cabbages, and cucumbers, healthy oregano shoots should attract lacewing flies. These are likely to lay their eggs on the foliage of oregano and on nearby herbs. Eventually, the eggs should hatch into larvae that prey on caterpillars, aphids, and insect eggs.

8) Rosemary (Salvia rosmarinus)

Rosemary naturally repels caterpillars for 3 major reasons. First, its leathery leaves may be too tough for larvae to feed on and break down. It would require too much energy and strength for caterpillars to spend their time feeding on the needle-like foliage, especially if there are softer leafy plants around the area.

Second, rosemary leaves are bitter and aromatic due to their essential oils. Packed with potent phytochemicals, these are regarded as inedible by many insects. Their scent alone, though appealing to us, can mask the scents of nearby crops. Caterpillars are unlikely to make their way towards dense stands of this perennial. It would also be quite rare to see large ones hanging around mature rosemary shrubs.

Third, S. rosmarinus blooms attract many small birds like finches and sparrows. These are likely to peck at or feed on caterpillars. Situate rows of well-maintained rosemary shrubs around vulnerable crops in greenhouses, permaculture setups, or outdoor gardens. Even fresh cuttings of this herb can be spread around vegetables like lettuce and cabbage to deter any unwanted pests.

9) Plants that attract parasitoid wasps (various species)

Parasitoid wasps are insects that produce parasitic larval forms. When their eggs hatch, they release larvae that feed on caterpillars to survive. The eggs are either laid on the surface of larger caterpillars or directly injected into their bodies. Hosts of the parasitic larvae seldom ever make it out alive as their organs can become thoroughly consumed.

Growing plants that attract these fascinating insects is another nifty and sustainable means of reducing the chances of caterpillar infestations. Some of the best species are listed below. As the root systems of a couple of these plants emit destructive chemicals, make sure to double-check whether they may interfere with the growth of nearby crops. If they do, grow them in pots instead.

• Dill
• Yarrow
• Bishop’s lace
• Alyssum
• Coriander

10) Plants that attract birds (various species)

Wrens, tits, finches, songbirds, owls and so many more types of birds regularly consume caterpillars. A major, protein-rich component of their diet, caterpillars are often considered a prime choice by nesting female birds because they are easily palatable and jam-packed with nutrients. By growing plants that attract these birds, you will most likely see drastic reductions in your garden’s caterpillar populations.

Plants that attract birds come in all sorts of forms. These include trees, densely flowering herbs, towering shrubs, and even epiphytes like orchids. Maintaining a diversity of these should help boost your property’s avian populations and increase their diversity. They may not directly repel caterpillars, but they do indirectly manage their spread in a more ecologically balanced and sustainable manner.