Often mistaken as bees due to their patterns of yellow and black stripes, hornets are actually a type of wasp. Listed under the Vespa genus, these are mostly found in tropical Asia and in some parts of Europe and North America. Known as social insects, they create shared nests in woody plants and in some underground locations. They aggressively guard their nests, ready to defend their queen and their young when threats arise.
Hornets are typically perceived as pests because they are able to sting repeatedly. Unlike bees, these insects don’t lose their stingers or subsequently die soon after contact. Moreover, hornet stings are more painful and dangerous than those of bees because of their highly potent venom. While their venom isn’t necessarily deadly, it can be fatal to humans who are inherently allergic to stings.
Although hornets don’t deliberately sting humans, simply grazing their nests by accident can release pheromones that may cause them to attack. For general safety, it would be prudent to minimize the occurrence of hornets in residential properties, especially in gardens that are frequented by pets and children. The plants listed below should help reduce your chances of encountering hornets in your own backyard.
1) Pennyroyal (Mentha pulegium)
Pennyroyal is a remarkably fragrant member of the Lamiaceae family of mint plants. It occurs as an annual or perennial herb along moist locations, such as the borders of ponds and the margins of calm streams. Seasonal dampness aids in the colonization of disturbed locations, which include roadsides and abandoned agricultural fields. In some parts of the US, it spreads quickly enough to be an invasive plant.
The strong aroma of pennyroyal, which is given off when the leaves are crushed or blown in the wind, is precisely what repels hornets and many other types of wasps. These scent-sensitive insects tend to be attracted to some fragrances, but they are definitely turned off by those of mint species. Moreover, the summer blooms of this species can attract beneficial insects that may parasitize on and compete with hornets.
If your garden has water features, this would make a fine, pest-repellent choice for its dampest areas. Make sure to situate it in substrates that receive consistent moisture all throughout the year. If you’re concerned about its capacity to spread, you can also restrict its roots to within pots and containers. Potted pennyroyal, especially those with sustainably harvested leaves, should continue to be effective as a hornet-repellent.
2) Lavender (Lavandula spp.)
Prized for their ornamental qualities, tolerance for dry conditions, and ease of care, lavender species are some of the most useful plants to grow in areas with mild climates. These sun-loving herbs are set apart by their greyish-green foliage and their purple floral spikes. These can add a romantic touch to cottage gardens and semi-arid backyards.
Though lavender species tend to attract bees and other pollinators with their strong scent, they are generally disliked by hornets and other wasps. The scent is generated by their essential oils, which contain high concentrations of insect-repellent compounds. These include phytochemicals like linalool, camphor, and limonene, which are common ingredients in botanically-friendly insecticides.w
If lavender is difficult to grow in your area, perhaps due to high humidity or poor sun exposure conditions, consider using its pure extracts. Mix these into a water-based spray and target plants that may be favored by hornets as nesting sites. Apart from repelling hornets, this spray should help control local populations of mosquitoes, flies, ticks, and more.
3) Rosemary (Salvia rosmarinus)
Widely cultivated as a culinary herb, rosemary can bring a wealth of ecological benefits wherever it is grown. Its tough, drought-tolerant shoots become increasingly woody, adding vertical structure to an herb garden. Their needle-like and leathery foliage is both decorative and functional. They contain a fragrant and flavorful essential oil – one which likely evolved to protect the plant from potential grazers and pests.
Often described as strong and woody, the scent of rosemary cuttings can help deter hornets and other types of wasps from creating nests in your garden. Rosemary can be grown around other plants that may attract wasps, especially as its scent is usually overpowering enough to mask those of other herbs. As its upright shoots can level off at around 4 feet (1.2 meters) or more, they can even be encouraged to form a natural barrier.
Rosemary grows best in mild, temperate climates, where its shoots can produce their eye-catching blooms from spring to summer. It tends to thrive in coastal locations with calcareous and sandy substrates. It can be quite challenging to grow in tropical locations with moist conditions, including those where hornets may thrive. As an alternative, you may opt to search for its pure extracts to create a hornet-repellent, water-based spray.
4) Common sage (Salvia officinalis)
A congener of rosemary, the common sage shares many of its pest-repellent features. It also makes for a stunning ornamental plant and culinary ingredient. The fuzzy, grey-green foliage of this herb is associated with many miraculous effects, including the ability to heal snakebites and fend off evil spirits. Of course, these are largely anecdotal; however, they may have some truth to them as this herb contains a chemically powerful essential oil.
Released by the plant when its leaves are crushed or rubbed, sage essential oil is remarkably fragrant and bitter when consumed in its raw form. It contains many phytochemicals that function as natural insect repellents and antioxidants. These include thujone, camphor, and 1,8-cineole. Collectively, these protect the foliage from potential herbivores, like deer and rabbits. They also have a knack for repelling troublesome insects, like pestilent flies and hornets.
A fairly low-growing herb, sage can be used as a ground cover plant. Its many attractive cultivars, which produce leaves with various colors and variegation patterns, can draw attention to partly shaded gardens. These can be grown around the base of shrubs or trees that may require added protection from pests.
5) Wormwood (Artemisia absinthium)
Hornets simply can’t stand the strong and astringent scent of wormwood, which is frequently grown as an ornamental plant in herb gardens. Often used as a prime example of toxicity in plants, wormwood produces a highly potent and pharmacologically-valuable essential oil. Rich in thujone, which can be dangerous in large doses, it has potential as a botanical insecticide. Its cuttings can be spread around areas that are frequented by wasps, flies, and ticks.
Wormwood is a fascinating plant to cultivate in just about any type of garden, but it is not particularly ideal as a pest-repellent addition to backyards with pets and children. You may wish to elevate its shoots with the use of tall pots. This way, unsuspecting pets or small grazers are not directly exposed to its toxins.
As a wasp deterrent, wormwood would be most effective if it is situated in bright areas and grown in fertile, well-draining substrates. Rich nitrogen concentrations in dedicated nursery beds should work best. Note that this species does not perform favorably if it is grown as a companion plant next to other species with contrasting preferences. Well-maintained, single-species stands would work best.
6) Citronella grass (Cymbopogon nardus)
Known for its useful properties as a natural mosquito repellent, citronella produces a fragrant essential oil with a lemon-like scent. In the wild, fields of this grass are rarely visited by scent-sensitive insects and grazers. In fact, even livestock are unable to use its unpalatable foliage as a source of nutrients. Mechanically damaging or rubbing the leaves releases their insect-repellent oils. Pure extracts can be incorporated into candles or added to flammable coils to create portable repellents.
If you have a wildlife garden that is plagued by many undesirable insects, you might consider growing a few stands of this species. Its strong fragrance should mask the scent of plants that may attract wasps. Do keep in mind, however, that it may spread in optimal conditions. If you’d like to keep its spread to a minimum, particularly in ornamental setups, you may grow it in pots or containers.
Hornets and their close relatives, such as yellowjackets, are unlikely to approach areas that smell of citronella grass. Other species under the Cymbopogon genus should be similarly effective at repelling wasps. Their essential oils can be incorporated into environmentally-friendly and water-based repellent sprays.
7) Marigold (Tagetes spp.)
Marigolds bring a wealth of benefits wherever they grow. Their vivid, yellow-to-orange blooms attract tons of beneficial insects while repelling unfavorable ones. This way, these fragrant, musky plants aid in the control of pest infestations. Oftentimes, the scent given off by damaged marigold leaves is strong enough to mask the scent of sweet-smelling plants that may attract wasps and flies.
The most commonly grown types of marigolds are the French marigold (T. patula) and African marigold (T. erecta). These may be quite effective at deterring hornets, though their congeners should be helpful as well. Just make sure you won’t be growing a marigold cultivar that has been developed to be scentless. Take note that the strong scent, though it may be unfavorable to some people, is key to warding off pests.
Reliable and bold, marigolds are great to have in private gardens and parks because they are low-maintenance and versatile. Grow them alongside other wasp-repellent plants, particularly those which share their basic preferences, for best results. Though hornets don’t like marigold blooms, take note that nectar-loving bees do.
8) Basil (Ocimum basilicum)
One of the world’s most important culinary herbs, basil is loved by chefs and gardeners alike for its strong scent, complex flavor, and delicate leaves. With cultivars that grow anywhere from 1 to 5 feet (0.3 – 1.5 meters) tall, it is a remarkably versatile plant for hot and dry locations. It favors conditions in warm regions that are often frequented by problematic hornets, making it an ideal deterrent for wasp-repellent gardens.
The mechanism by which basil repels pests is its fragrant essential oil. Simply rubbing the leaves releases their scent, so collecting a few cuttings emits a scent cloud that can overpower a room or small garden. Regularly harvesting your basil plants is perhaps the most environmentally-friendly means of repelling wasps and potential grazers.
The essential oil of basil leaves contains linalool, cineole, and estragole. To an extent, these chemicals can collectively function as a mosquito-repellent and can even kill insect larvae upon contact. Pure extracts can be distributed around key entry points of a home or garden. This should discourage many pests from entering your property and nesting in the garden.
9) American wintergreen (Gaultheria procumbens)
Known for its excellent resistance to pests, wintergreen is a vigorous and evergreen shrub with fantastic ornamental properties. Also known as the boxberry or the eastern teaberry, it is an excellent choice for small to medium-sized gardens. Its shoots grow to a maximum height of just 6 inches, making them easily manageable. Low-maintenance, this species is a recipient of the RHS Award of Garden Merit.
The most eye-catching features of the American wintergreen are its dainty summer blooms and its vivid, red berries. The fruits are favored by many endemic mammals, including the black bear and white-tailed deer. Though it appeals to these valuable wild animals, this plant is generally avoided by scent-sensitive insects. Hornets are unlikely to nest close to their extensive stands because their leaves emit a distinctly minty and strong scent.
10) Eucalyptus (Eucalyptus spp.)
Eucalyptus trees have a wealth of natural adaptations, making them some of the most resilient plants throughout their native range. Several species are adapted to withstand extreme heat, including those given off by wildfires, whereas others have fantastic resistance to pests and diseases. These plants generally have valuable timber and essential oils.
The essential oil of eucalyptus, which is now predominantly sourced from the southern blue gum (E. globulus), functions as a natural insect repellent. It also has potential as a biopesticide and is commonly used as a fragrant ingredient in soaps, lotions, and perfumes. Due to its overpowering aroma, hornets and other wasps are likely to avoid eucalyptus foliage and shoots.
Eucalyptus trees can serve as multi-functional additions to backyards in developed areas. Their canopies can provide shade from the heat while minimizing the chances of insect infestations. Their attractive bark can also bring year-round interest while adding a vertical dimension to planted landscapes. If you intend to grow these plants for their many benefits, make sure to select non-invasive species.
