Aphids are tiny bugs that belong to the family Aphididae nestled within the order of the true bugs, Hemiptera. They are common garden pests that feed on the new growth of plants and reproduce quickly due to their ability to reproduce asexually.
A few aphids are generally acceptable for established plants, but if left unmanaged, their populations can increase dramatically and overwhelm plants. In some cases, even a few aphids can be an issue because they are vectors for plant diseases. Additionally, the sugar-rich honeydew that aphids produce will attract ants and provide nutrients for sooty mold growth, which can inhibit photosynthesis.
One way to reduce the number of aphids in a garden and prevent population explosions is by attracting natural enemies, either insect predators or parasites, to the garden. The larvae of lady beetles, lacewings, and syrphid flies, for example, are voracious predators of aphids. These insects lay their eggs on leaves near a source of aphids or other prey items. Lady beetles produce a cluster of orange eggs, lacewings leave behind eggs on a thin strand, and syrphids lay simple white eggs. Soldier beetles will also defend a garden against aphids.
Most natural enemies visit plants searching for nectar and pollen, so they are attracted to the same flowers that draw in pollinators and pests. However, some natural enemies, like parasitoid wasps, can be attracted to the waste products of their prey. For example, some adult species eat honeydew produced by the same aphids they will parasitize. Other parasitoid wasps react to chemical cues produced by plants actively fed on by pests.
1) Dill (Anethum graveolens)
Dill is an herb that produces many small, yellow flowers in clusters called umbels. These vibrant flower clusters are attractive to ladybugs, lacewings, and parasitic wasps. At the end of the growing season, the flowers turn into seeds that can be replanted in the next growing season.
Dill thrives in zones 3 to 7 and can be grown in the winter in zones 9 to 11. The plant is native to southwestern Asia, although it was introduced and has become naturalized throughout North America. As a result, dill does best during the summer in areas with full sun, plenty of water, and well-draining soil.
2) Fennel (Foeniculum vulgare)
Fennel is another perennial herb that produces large, yellow flowers in umbel clusters. It is a close relative of dill, with the plant and its seeds used as a common spice. Their flowers attract hoverflies, parasitic wasps, and ladybugs. Fennel comes in two broad varieties: herb fennel and vegetable fennel, with the former grown for its seeds and the latter as a leafy green.
This plant grows best in zones 4 through 9 and will return year after year in warmer climates. It can grow in colder regions but is likely to die off during winter freezes. Wet conditions are best for this plant, although fennel needs well-draining soil to avoid root rot.
3) Yarrow (Achillea millefolium)
Yarrow is a hardy, perennial herb that produces clusters of small, white, pink, red, or yellow flowers that attract beneficial insects such as ladybugs, hoverflies, and lacewings. It is tolerant of frost due to its fern-like leaves. The plant also possesses nectaries that are attractive to natural enemies.
The herb is bitter and is valued as an essential medicinal and cultural herb. It is naturally found in Europe and through zones 3 to 9 of North America. Like many other herbs, yarrow is drought- and frost-tolerant, making it easy to grow and care for. However, it requires full sun and well-draining soil.
4) 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 an easy plant to grow in zones 5 to 9 and produces many clusters of small, white flowers that attract hoverflies and lacewings, which predate upon aphids. 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.
5) Sunflowers (Helianthus spp.)
Sunflowers are famous for their large, showy flowers that produce edible seeds loved by humans, birds, squirrels, and aphid predators. Bees, ants, and other pollinators also belove 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.
6) Clover (Trifolium repens)
Clover is a legume that produces small, white, or pink flowers that attract beneficial insects such as ladybugs, hoverflies, and parasitic wasps. Clover lawns are growing in popularity due to their low-maintenance nature compared to traditional American grass lawns. A clover yard requires minimal watering and minimal mowing, does not require fertilizer, and attracts its own natural enemies, reducing insecticide costs. Aphids are attracted to clovers, and so aphid predators who come to feast on clover nectar also take advantage of any available prey.
7) Fava beans (Vicia faba)
Fava beans are another legume that produces large, showy flowers that draw in aphid predators. The white flowers with black centers grow in clusters along the stem. The crimson-flowered fava bean produces beautiful red flowers. Additionally, their seeds are edible when cooked.
Like sunflowers and yarrow, fava beans have nectaries that provide food for aphid predators and pollinators. These tall plants require some support, especially when the heavy bean pods begin to develop.
8) Cosmos (Cosmos spp.)
Aphids feed on cosmos, but they possess chemical compounds, like phenolic acids, that attract natural enemies like ladybugs and spiders that defend a garden from pests. This plant produces simple, flat flowers that come in various colors. They can be grown in the spring and fall in most growing zones and during the summer in cooler regions of North America.
Cosmos can be started indoors or sown directly into the ground. It will take around three months for it to produce beautiful blooms. Natural enemies are attracted to the cosmos’ vibrant flowers, and the seeds planted after the colors are spent can be saved for the next season.
9) Queen Anne’s lace (Daucus carota)
Also known as wild carrot, the annual queen Anne’s lace is a member of the umbellifer family and produces delicate white flower clusters at the top of the plant. The plant is entirely edible, although it contains the toxin falcarinol, which can be toxic if eaten in excess. It attracts a variety of pests and pest predators, including aphids and their predators.
Queen Anne’s lace blooms in the fall and summer, with the ideal planting time occurring after the danger of frost has passed. Queen Anne’s lace can quickly take over a garden as a weedy plant, so measures should be taken to contain it when planted.
