Wasps have an undeserved bad reputation among people. When people think of wasps, they envision their aggressive behavior when people get too close to their nests. However, wasps are incredible insects with essential ecosystem services such as controlling other insect populations. Without wasps, farmers would need to use more toxic pesticides to control the insects that eat crops and carry diseases. Some wasps also pollinate; hunting adults (adult wasps seeking food to feed their developing brood) gather and eat sugar from the nectar of flowers. They pollinate any flower, unlike bees that prefer certain colors and shapes of flowers to collect nectar.
As ecologically important wasps are to humankind, it is not ideal to have a wasp nest in a backyard. They will sting animals and humans as a defense to protect their territory, nests, and themselves. Their behavior is no different from a human taking care of their home, family, and well-being. In the same manner humans respect each other’s space, wasps need respect and space to perform their ecological services. There are many ways to prevent wasps from nesting in a backyard, such as patching up cracks, keeping food and trash covered, covering holes, and removing food sources.
The following list describes 8 effective wasp-repelling plants to place around the house or on the porch. Planting wasp-repellent plants is a simple and effective method to prevent the unnecessary eradication of wasp nests. It is important to keep in mind if the species of wasp deterring plants are native, as invasive ornamental plants can disturb the ecological niches of insects, reduce native plant diversity, and reduce the quality of wildlife habitat.
1) Wormwood (Artemisia absinthium)
- Family: Asteraceae
The name “wormwood” is derived from the German word “Wermut” meaning “keeping a clear mind.” Some other common names are absinthe, maderwood, absinthium, and absinthe wormwood. It is a shrub-like perennial growing to a height and width of 80 cm (2.6 feet). The leaves are silvery-green, alternate, broadly ovate, and finely divided into narrow segments. Their length is between 1 – 3 inches (2.5 – 7.6 cm), with a width of 0.5 – 1.5 inches (1.3 – 3.8 cm). Basal leaves tend to be larger and deeply lobed, while upper leaves are smaller and more simple. The leaf surfaces are covered with silver hairs on both sides of it. It is very soft to the touch and most of the leaves have a strong scent that deters wasps from flying near it.
This plant is easy to grow in a sunny, well-drained spot. Some excellent spots to plant it are in garden beds, borders, or rock gardens. While wormwood is native to Europe, it was introduced to the United States in 1841. It was banned at the beginning of the 20th century as a consequence of its adverse effects used in alcoholic drinks such as vermouth and absinthe. Its oil contains the chemical thujone, which can cause seizures at a high dosage, although some people use wormwood for digestion problems, osteoarthritis, Crohn’s disease, kidney disorders, minor wounds, and insect bites. Wormwood oil is also used as a fragrance component in soaps, cosmetics, and perfumes. The ban was uplifted in 2007 and it is now naturalized in North America.
Today, there is more research on the biological activity of the components of this species such as antibacterial, anti-ulcer, anti-inflammatory, cytotoxic, neuroprotective, antidepressant, neurotrophic, procognitive, cell membrane stabilizing, and antioxidant activities.
2) Mint & spearmint (Mentha & Mentha spicata)
- Family: Lamiaceae
The name “mentha” is the Latin name for an unfortunate Greek nymph named Mentha, who was turned into a mint plant! Mint has a genus of 25 species of fragrant herbs. It is native to Eurasia, North America, southern Africa, and Australia. One of the species, Mentha spicata, “spicata” meaning spearmint, is commonly used for foods and liqueurs. Spearmint is native to Europe and Asia and has been naturalized in North America and some parts of Africa.
Mints have square stems and opposite aromatic leaves. They can spread by stolons in zones 9 – 11, which can be aggressive in gardens. They have small flowers that are pink, pale purple, or white, and are arranged in clusters, forming whorls or clumped together in a terminal spike. The flowers are not typical to other family members, sometimes having more than five petals. The volatile oils are contained in resinous dots in the stems and leaves.
Spearmint is a perennial plant that grows up to 90 cm (3 feet). It aggressively spreads by creeping stolons. It is best to keep these shade-loving plants in pots or containers before they outcompete other plants in gardens. The simple fragrant leaves are sharply serrated and arranged opposite the square stems. Its scent is attractive to pollinators, but to wasps, they are foul-smelling plants. Spearmint has tapering spikes of white, lilac, or pink flowers.
3) Pennyroyal (Mentha pulegium)
- Family: Lamiaceae
The pennyroyal is a perennial mint native to the Middle East, Europe, and North Africa. It has been introduced to the Americas, parts of Asia, Mozambique, New Zealand, and Australia. It is a minor weed in Australia and New South Wales.
This perennial herb has creeping and erect stems. The stems are hairy when aerial, and hairless when submerged. Leaves are about 1 – 2.5 cm (0.4 – 1 in) long and are smaller higher up the stem. The leaves are narrowly ovate to elliptic, base tapered to obtuse, tip rounded, and margin entire to finely serrate. The flower is 2 – 4.5 cm (0.8 – 1.8 in) long with 5 lobes. They appear purple and hairy and are dotted with glands on the outside, with a prominent white hairy tuft in the throat. It gives off a strong mint scent that when crushed, wasps and other insects cannot stand it. It thrives in poor soil and moist conditions and spreads relentlessly. It is best to place these aggressive spreaders in containers.
Pennyroyal is used as an insect repellent and abortifacient. When taken by mouth, it is highly toxic and linked to liver injury, seizures, and death. This is due to the volatile oil pulegone and other monoterpenes. Pennyroyal extracts are used in aromatherapy, but should never be ingested. Glutathione has been shown to detoxify the toxic metabolites of pulegone, and N-acetylcysteine should be administered if pulegone is accidentally consumed.
4) Common thyme (Thymus vulgaris)
- Family: Lamiaceae
The common thyme was previously known as Organum thymus and Thymus collinus. The word “thymos” means “perfume” in Greek and “vulgaris” means “common” in Latin. The origin of the word “thyme” is from the Greek word thumos, meaning “courage.” During medieval times, thyme was symbolic of bravery.
The common thyme is a dwarf, low-growing shrub and is commonly cultivated as an annual, though it can persist as a perennial in warm climates. Thyme is native to Eurasia and is cultivated throughout the world. It is used to flavor foods and Benedictine liqueur. Its essential oil, thymol, is used in perfumes and dentifrices. Many are grown as ornamental ground covers.
Thyme grows 8 cm (3 in) tall and will spread over time by rooting stems to 30 cm (12 in). It performs best in dry, rocky soil and prefers full sun and good drainage. Some recommended spots to grow thyme are beds and borders, cottage gardens, containers, and Mediterranean gardens. Thyme stems are woody and have simple leaves that are oval to linear and arranged oppositely. The tiny tubular flowers are created in whorls along the stems, usually white or purple. Bees are attracted to the flowers, but wasps greatly dislike them (and it is deer resistant, too!). Thyme’s scent and flavor are at their strongest when the leaves are fresh and young. For a reliable wasp deterrent, makes sure to snip off any old growth.
5) Basil (Ocimum basilicum)
- Family: Lamiaceae
Basil, also known as sweet basil, is widely cultivated for its edible leaves. The term basil is used for the scented leaves that bees and wasps dislike, and is mostly used for culinary purposes. Basil has a long history of usage. It was known as the “royal herb” in ancient Greece and was used in medicine and religious practices.
Basil is a low-growing herb that thrives in warm, tropical climates. The perfect spots to plant basil are containers or window boxes. It is native to India and other tropical regions of Asia, where it has been cultivated for more than 4,000 years. Basil grows between 30 – 60 cm (1 – 2 ft) tall with opposite, light green, silky, flat, shiny leaves. The leaves are 3 – 7 cm (1.2 – 2.8 in) long and 1 – 3 cm (0.4 – 1.2 in) broad. The flowers are large, white, and arranged in a terminal spike. Unlike other species in Lamiaceae, the four stamens and the pistil are not pushed under the upper lip of the corolla but lay over the inferior.
Other basils are grown in many regions of Asia. They have a clove-like flavor that is generally stronger than the Mediterranean basils. The most notable species are holy basil or tulsi. Sweet basil has traditionally been used for the common cold, muscle pain, insect bites, bronchitis, and influenza. There is much research into the health benefits of essential oils, including basil oil. Studies show that it has potent antioxidant, anti-cancer, anti-viral, and anti-microbial properties.
6) American marigold (Tagetes erecta)
- Family: Asteraceae
The genus Tagetes is named after an Etruscan deity “Tages”, and erecta means “upright.” Its other common names are African marigold, Aztec marigold, Mexican marigold, and big marigold. Marigolds are a frequently cultivated, flowering herbaceous annual or houseplant, known for their large flowerheads. They typically grow 1 – 4 inches (2.5 – 10.2 cm) tall and have huge, double-globular flowers that are 2 – 4 inches (5.1 – 10.2 cm) in diameter and come in various shades of orange, yellow, and hints of white. The leaves are pinnate on glabrous, angular stems.
Tall varieties may need staking, and old flowers should be deadheaded since they are heavy and may cause the stems to snap. The foliage and flowers have a strong spicy scent that keeps wasps away. Triploid F1 hybrids (T. erecta x T. patula) combine the large flowers of the American marigold with the compact size of the French marigold into vigorous plants with 2 – 3 inches (5.1 – 7.6 cm) in diameter flowers on stems rising 10 – 18 inches (25.4 – 45.7 cm) tall. The triploids are unaffected by the summer heat and bloom throughout the summer. Some spots to plant marigolds include edges, beds, and containers.
7) Geranium (Geranium maculatum)
- Family: Geraniaceae
Geraniaceae contains more than 600 species worldwide that range from small herbs to succulent shrubs. The garden geranium belongs to the genus Pelargonium. There are 50 species and varieties that are known in North America and Hawaii, including introduced weeds.
The geranium grows from thick rhizomes that are usually under a thin layer of soil. A single plant can spread 60 – 100 cm (2 – 3 ft) in diameter. Palmated, dissected, and tooth leaves emerge in late spring. The leaves are 8 – 10 cm (3 – 4 in) in length and width. Summer leaves are 15 cm (6 in) long and wide. Flowers are produced in small clusters at the end of long stems. The flowers are rose-purple and 2.5 – 4 cm (1 – 1.6 in) wide. Flowers bloom from April – July, depending on their location. It is commonly known as the crane’s bill because of the shape of the fruit before it releases its seed. The fruit is typically composed of five sections that form a point, with a shape similar to a crane’s bill. When the fruits ripen, the sections spring upward and throw the seed away.
Geraniums are found in forests, fields, thickets, and meadows. As a classic garden plant and absolute favorite among gardeners, geraniums can be planted in hanging containers, beds, window boxes, and borders. Its scent deters wasps through the chemicals in the oil molecules such as geraniol, linalool, citronellol, and nerol. The essential oil is highly sought out for its purported health benefits such as lowering stress, boosting immunity, lowering inflammation, aiding digestion, skin, and hair, and reducing nosebleed severity.
8) Lemon grass (Cymbopogon citratus & Cymbopogon flexuosus)
- Family: Poaceae
Cymbopogon citratus is derived from the Greek words “kymbe” and “pogon” which means boat and beard, respectively. This refers to the flower spike arrangement. The genus Cymbopogon belongs to the grass family, Poaceae. The Poaceae family has 700 genera and 11,000 species distributed throughout the world. The two well-known species are the West Indian lemon grass (Cymbopogon citratus) and East Indian lemon grass (Cymbopogon flexuosus). The West Indian lemon grass has its origins in Malaysia, while the East Indian lemon grass has its origins in southern India.
Cymbopogon plants are tall perennials and fast-growing, with a tuft of lemon-scented leaves from the annulate and sparingly branched rhizomes. It grows to a height of 1 m (3.3 ft) and a width of 5 – 10 mm (0.2 – 0.4 in). It has bluish-green leaves that do not produce seeds and bulbous stems that increase the clump size as the plant grows. The leaves are long, glabrous, glaucous green, linear, tapering upward and along the margins, with short ligule and tightly clasped sheaths at the base, narrow and separated at the distal end.
Both species give off a strong lemon scent that deters wasps. Lemon grass oil is used to fragrance soaps, deodorants, and cosmetics. Upon steam distillation of dried leaves, a yellowish-colored, strongly fragrant liquid oil, known as cochin oil in world trade, is obtained, which has properties attributed to its strong chemical composition. The active ingredients present are myrcene, limonene, citral, geraniol, neral, nerol, citronellol, and geranyl acetate, which are antimicrobial and insecticidal. This oil combats bacteria, fungi, and insects. The chemicals within the oil may help relieve pain and swelling, improve sugar and cholesterol levels, reduce fever, stimulate the uterus and menstrual flow, and have antioxidant properties.
