The term “beneficial insect” can refer to many insects, although they generally fall into two broad categories, natural enemies or pollinators. The former group includes insects like ladybeetles, mantids, hoverflies, dragonflies, spiders, and lacewings, whereas the latter contains insects like butterflies and bees.
Some insects, like wasps, are both pollinators and predators. For example, large wasp species, like the paper wasp (family Vespidae), hunt other insects to feed their larvae while the adults consume nectar from flowers and pollinate them in return.
Generally, beneficial insects are attracted to flowers and variety in a garden. However, some plants also release chemical attractants when damaged, indicating to insect predators that a meal is present. For example, in the case of the tomato hornworm (Manduca quinquemaculata), a type of caterpillar, damage caused by the worm attracts a parasitic wasp that lays eggs inside of the worm. These eggs then develop and emerge from the caterpillar as adults.
1) Dill (Anethum graveolens)
Dill is an herb that produces small, yellow flowers in clusters called umbels. These flowers are attractive to beneficial insects like ladybugs (family Coccinellidae) and hoverflies (family Syrphidae). It is also a host plant for the larvae of some beneficial insects, including the black swallowtail butterfly (Papilio polyxenes). Dill is also high in vitamin C and other nutrients, making it a great meal addition. It is excellent in pesto, potato salad, chicken, and fish. Growing dill is easy, and there are many varieties to pick from that vary in overall size, leaf size, and number of flowers.
2) Fennel (Foeniculum vulgare)
As another umbellifer, fennel produces flower clusters called umbels and is another herb with tiny flowers that attract beneficial insects, including parasitic wasps and ladybugs. Additionally, like dill, black swallowtails use fennel as a host plant. Finally, fennel seeds are a commonly used spice added to dishes to provide a sweet taste to curries, desserts, and bread.
As with other Mediterranean herbs, fennel should be grown in full sun in soils that are well draining. They can be grown indoors to get ahead of the growing season, but they are not the best herb to transplant to the garden because they develop a tap root as seedlings. Therefore, sowing them directly into the garden or starting them in a large pot indoors is best.
3) Yarrow (Achillea millefolium)
A close cousin of fennel and dill, yarrow produces umbels with yellow, white, or even pink flowers. In addition to attracting beneficial insects, including lacewings, ladybugs, and hoverflies, yarrow is often used as a natural remedy for minor illnesses. It grows best in zones 3 to 9 in sunny, hot, and dry environments. Yarrow does not tolerate constantly wet conditions. As long as these conditions are met, yarrow is an easy herb to grow that does not require much maintenance.
4) Goldenrod (Solidago spp.)
Next up are the asters (Asteraceae). Asters are a highly speciose group of flowering plants with many different plant forms and flower colors. For example, members of the genus Solidago have bright, yellow flowers which can attract a wide range of beneficial insects, including ladybugs, lacewings, and parasitic wasps. These organisms are attracted to the plentiful nectar the aster provides and will happily scarf down any pests they stumble across. Generally, goldenrods naturally occur throughout North America, and gardeners can find a variety that suits their yard relatively easily.
5) Sweet alyssum (Lobularia maritima)
This next annual is a member of the Brassicaceae family, making it a close relative of the Brassicas, a group containing cauliflower, broccoli, brussels sprouts, and other common vegetables. Sweet alyssum is known as an easy plant to grow in zones 5 to 9 and produces many clusters of small, white flowers that attract hoverflies and lacewings. In addition, many cultivars have pink, purple, or even orange blooms. Sweet alyssum can be started indoors up to 6 weeks before the last frost date. Then, another round of seeds can be planted in the fall for a second growing season.
6) Salvia (Salvia spp.)
Salvia produces spikes of blue, purple, and pink flowers that look similar to lavender flowers and are attractive to bees and butterflies. The plant blooms in late spring and throughout the summer and is a popular choice for herb gardens. Additionally, perennial and annual varieties have many different growth forms (i.e. bushes, shrubs, and single plants). They are incredibly drought-tolerant and are perfect for low-maintenance landscaping. Generally, they can survive off rainwater alone, although gardens in arid states may benefit from the occasional watering.
7) Phlox (Phlox paniculata)
Phlox produces fragrant clusters of flowers in shades of pink, purple, and white. These clusters are attractive to bees, butterflies, and hummingbirds and bloom in mid-summer. It is a perennial plant, too, and will return year after year. Phlox flowers are also deer-resistant.
Many varieties thrive in various climates, from the sun-loving tall phlox to the shade-tolerant woodland phlox. In addition, phlox is easy to grow from seed, transplant, and even cuttings. Another trait that makes this an attractive option for homeowners is that it is not toxic to pets, so dogs and cats can ingest phlox without falling ill, making the plant a pet-safe alternative for other poisonous garden plants.
8) Cilantro (Coriandrum sativum)
Cilantro is often used in companion planting wherein gardeners plant trap crops or plants that attract beneficial insects with other plant species that may be more vulnerable to pests. This is due to its tendency to attract lady beetles, lacewings, and parasitic wasps to the home garden, ensuring that populations of soft-bodied pests remain under control.
Additionally, cilantro allowed to grow to maturity produces beautiful, delicate white blooms that can be used in cooking as a spice like the rest of the plant. Luckily for home gardeners, cilantro is an easy herb to grow and enjoys full sun, well-draining, and slightly acidic (pH 6.5 – 6.8) soil. This plant also needs fresh compost when planted.
9) Sunflowers (Helianthus spp.)
Sunflowers are famous for their large, showy flowers that produce edible seeds loved by humans, birds, and squirrels. Bees, ants, and other pollinators also love them. The flowers bloom in the summer and fall and can be used for cut flowers or as a source of edible seeds if allowed to dry out.
Some varieties are bred for seed production, like the mammoth sunflower, which can grow over 12 feet tall. Others are purely decorative, like the dwarf sunflowers. All sunflowers possess nectar-producing structures known as nectaries that attract insects, primarily ants, to the flower even before it blooms. This ensures that pollinators will be present on the plant when the sunflower blooms for timely pollination. Ants will also protect sunflowers from other animals.
10) Coneflowers (Echinacea purpurea)
Purple coneflowers are another aster species with purple flowers and petals that droop as the flower ages. There are many different coneflower cultivars with varying colors of flowers, including white, pink, and yellow. Generally, this species blooms once a year in the summer but may also produce blooms in the fall, depending on the climate. Purple coneflower blooms last for up to two months.
To grow purple coneflowers in the home garden, one should plant them in full sun. While they can survive in areas with shade, the fullest blooms will be achieved in locations with full sun. Purple coneflowers proliferate in warmer months. After the flowerheads have been spent, the remaining seeds attract songbirds, like the American goldfinch (Spinus tristis), which eat them and are a colorful sight in the home garden. Interestingly, specially prepared Echinacea roots are used as an herbal remedy to boost the immune system.
Why Are Beneficial Insects “Beneficial”?
Beneficial insects are fantastic guests in the home garden because they play critical roles in natural pest control, pollination, biodiversity, and the function of nearby native ecosystems. For example, a flight of dragonflies may not eat aphids hidden under leaves, but they do considerably dent the local mosquito population. For example, ladybugs and lacewings can eat large numbers of aphids, while parasitic wasps can lay their eggs inside other insects, eventually killing the host insect. In addition, predatory insects maintain pest populations, ensuring that pest populations are less likely to explode and overwhelm plants.
When a gardener sees an infestation, the gut reaction is to spray the infestation with an insecticide, but these chemicals are often non-specific and will damage beneficial insect populations. This reduces biodiversity and decreases the garden’s resilience against future pest outbreaks. By attracting these natural enemies, you can reduce the need for harmful pesticides and protect your crops from pest damage. Additionally, reducing your reliance on pesticides can promote a more sustainable approach to gardening and farming. Finally, attracting natural enemies to your yard is generally considered a safer and more sustainable approach to pest control than using pesticides.
