Companion planting isn’t just about planting flowers that look good next to each other. When choosing companion plants to complement a dahlia, look for plants that mutually benefit each other and aid in fighting off the dahlia’s common pests. Although companion planting is popular now among organic farmers because it often eliminates the need for fertilizers, companion planting is not a new phenomenon. Evidence of companion planting can be traced back to ancient Roman times and the Native Americans in the Americas.
Common roles of companion plants:
- Nurse plants serve as a breeding ground for favorable bugs that may eat common pests
- Trap plants lure pests away and sacrifice itself for the benefit of others. Some trap plants will also poison their prey.
- Strongly scented plants often deter unwanted pests.
When choosing your companion plants keep these facts in mind about the dahlia.
- Slugs, snalis, japanese beetles, and aphids are the dahlia’s common enemies.
- Dahlias generally grow several feet tall, so companion plants, if small, should be able to grow in partial shade.
- Dahlias repel nematodes (roundworms), so they will be of benefit to many herbs and vegetables.
Consider complementing and protecting your dahlias with a few of these plants.
The genus Artemisia includes many varieties with insecticidal properties. Plant a species of Artemisia, like wormwood or tarragon, to deter slugs. The strong scent of this shrub will help keep away the hated slug, probably the dahlia’s most feared pest. If you grow as a border around your garden, wormwood will deter animals as well.
Salvia, Flowering Sage
A member of the genus salvia, the flowering sage grows spikes or towers of flowers (look like rock candy) that attract hummingbirds and butterflies. Not only will they add beauty, but the butterflies and hummingbirds will eat aphids and beetles. Salvia grows in clumps and requires full sun, so don’t plant too close to the dahlias. The flowering sage come in different colors (red, white, blue, violet, and pink) and sizes (18 inches to 5 feet) so you can match appropriately with your dahilas.
Pronounced NAH-STIR-SHUM, this hardy annual is famous for growing almost anywhere. It repels black aphids and its leaves have a delicious peppery flavor that you can add to your salads. Their colorful flowers are also edible and make beautiful and delicious garnishes for soups, salads, deserts, fruit trays, etc. Most varieties will do well in partial shade. Great for bordering, these low-growing plants will provide a a colorful ground cover around or next to their taller neighbors.
Four O’Clocks and White Geraniums
These two both serve as a “trap crop” for japanese beetles, which means they will lure the beetles away from your dahlias. Both are also poisonous to the aphids if consumed. The Four o’Clock has beautiful delicate blooms but are tougher than they look, holding out for long stretches of drought and poor soil.
Red or Creeping Comfrey
These two ornamental varieties of the herb grow well in shade and deter slugs.
Coriander and Anise
Anise is a host plant for predatory wasps that kill aphids. Both coriander and anise deter aphids.
Growing these plants along with your dahlias will complement them aesthetically as well as protecting them from pests.
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Originally published at www.gardens.com.