The practice of pairing flowers with herbs, known as companion planting, creates a synergistic environment where different species support each other’s growth. This intentional grouping goes beyond aesthetic appeal, aiming to establish a healthier, more productive garden ecosystem. By strategically placing certain flowers next to culinary herbs, gardeners leverage natural biological interactions to improve plant vigor. This approach helps manage environmental challenges by optimizing the plant community’s composition.
The Practical Purpose of Pairing
The functional reasons for mixing flowers and herbs fall into two categories: natural pest deterrence and enhanced pollination. Many flowers release volatile organic compounds that act as natural insect repellents, effectively masking the scent of vulnerable herbs. The strong aroma of a flower can confuse pests that rely on smell to locate host plants, reducing the number of destructive insects nearby.
Other flowers act as “trap crops,” drawing specific pests away from the protected herb. These sacrificial plants localize the problem for easier management. Furthermore, nectar and pollen-rich blossoms serve as a food source for beneficial insects, such as ladybugs, lacewings, and parasitic wasps. These natural predators help regulate populations of common garden pests, like aphids and caterpillars, creating a balanced defense system.
Specific Beneficial Flower Recommendations
Marigolds (Tagetes spp.)
French marigolds are known for releasing a chemical called alpha-terthienyl from their roots. This chemical is effective at deterring nematodes, microscopic roundworms that attack plant roots. Planting them near basil can help protect the herb’s root system, while their pungent foliage also helps repel whiteflies from nearby plants. The vibrant blooms of marigolds attract hoverflies, whose larvae are predators of aphids.
Borage (Borago officinalis)
The star-shaped blue flowers of borage are highly attractive to bees, significantly increasing the pollination rates of neighboring herbs and vegetables. Borage is often planted near basil because it is believed to deter the destructive tomato hornworm. The plant’s deep taproot also helps draw up trace minerals from the soil. These minerals are then released when the plant dies back, benefiting shallow-rooted herbs.
Nasturtiums (Tropaeolum majus)
Nasturtiums are prized as highly effective trap crops, especially for aphids and the cabbage white butterfly. These pests find the plant’s foliage more appealing than many herbs, clustering on the nasturtium leaves instead. This allows the gardener to easily monitor and remove the pests without resorting to chemical sprays on their culinary herbs. They are commonly planted at the edges of herb beds to intercept early pest incursions.
Sweet Alyssum (Lobularia maritima)
The dense, low-growing clusters of tiny white flowers on Sweet Alyssum create a microclimate that supports minute beneficial insects. Its shallow, accessible flowers are an ideal nectar source for tiny parasitic wasps and hoverflies, which are natural enemies of aphids and other soft-bodied pests. Because it stays low to the ground, it acts as a living mulch that conserves soil moisture while drawing in pest control agents.
Important Considerations for Mixed Beds
Successfully combining flowers and herbs requires careful attention to their physical growing requirements to prevent competition. The most significant factor is matching water and light needs, as a single bed must accommodate all plants equally. Mediterranean herbs like rosemary, thyme, and oregano thrive in full sun and prefer sharp drainage and drier soil. This makes them incompatible with moisture-loving flowers such as impatiens or lobelia.
When designing a mixed bed, gardeners should ensure the soil depth is adequate, generally at least 8 to 12 inches, allowing both fibrous-rooted flowers and deeper-rooted herbs to establish. Proper spacing is necessary to prevent aggressive plants from overshadowing smaller, slower-growing herbs. Tall flowers should be placed to offer light shade to herbs that prefer a reprieve from intense afternoon sun, rather than blocking the light entirely.
Flowers and Herbs to Keep Separate
Some otherwise beneficial plants exhibit allelopathy, releasing chemicals that inhibit the growth of nearby plants. Fennel is the most notorious herb, chemically suppressing the growth of nearly all other herbs and flowers. It should be grown in its own dedicated pot or area, as this incompatibility can lead to stunted growth and reduced yields in neighboring plants.
Aggressive, rhizomatous flowers, such as certain varieties of bee balm or perennial sunflowers, should also be isolated. These plants spread rapidly via underground runners, quickly establishing a dense mat of roots that outcompetes delicate herbs for water and nutrients. To maintain a functional mixed bed, any plant known for aggressive spreading should be contained in a sunken pot or a separate garden barrier.