Tips for Designing with Dahlias

Dahlias, except for a few varieties, are large, nearly bush-sized plants with impressive blooms. When choosing what to pair with them, think about contrast, both in height and size, but also in texture and shape. Consider the following ideas to maximize space and add flower power without overwhelming the dahlias.

Plant Earlier Bloomers

Dahlias are eye-catching flowers, and you don’t want to steal their show, but they bloom later in the season. Many dahlias, especially dinner plate varieties, won’t produce flowers for 100 days or more after planting. In the meantime, early-blooming flowers like bee balm and peonies,can be mixed into the dahlia space, providing blooms, pollinator habitat, and interest while the dahlias grow.

Keep the Mature Size of Dahlias in Mind

Many dahlias, grown in fertile soil with adequate irrigation, will reach 4-5 feet tall or more, becoming very large plants. Some varieties resemble a mid-sized bush by late August. A low-growing sweet William or a French marigold may be completely eclipsed if planted underneath. 

Instead, strive for a layered effect, planting low-growing flowers and foliage at the edge of the bed and the dahlias in the center. In a pot, achieve the same look with plants that drape or trail over the edge.

Choose Plants with Similar Needs

Dahlias do best in full sun and moist, fertile, well-drained soil. Any flowers you choose to plant with them should enjoy the same. Plants that thrive in dry conditions or poor soil might not be a good match for dahlias. Plants that thrive in similar conditions eliminate problems later.

Most of us need to dig up our dahlias every fall and store the tubers indoors during the winter. Even in warmer zones, they will need to be lifted periodically to divide the tubers. If you have to tiptoe around a bunch of perennial plants, it makes the digging harder and damage to those perennials more likely.

In the immediate vicinity of the dahlias, stick with annuals. They’ll be done for the season at the same time as the dahlias, and it will be easier to get at the tubers when it’s time to dig.

A few pictures taken throughout the year can serve as an effective visual memory aid next year. Snap a picture in midseason, during full bloom, and towards the approach of the first frosts. You'll easily be able to see what worked, what color combos you liked, and what you might like to improve.

What to Plant with Dahlias

Based on the above considerations, here are some suggestions that work well as companion plants for dahlias.

Amaranth

Amaranth is available in drooping varieties or upright flower forms, makes an excellent addition to a dahlia bouquet, and is large enough to hold its own in the dahlia bed. The red varieties with burgundy leaves are an excellent contrast to dahlia foliage, and their unique blooms last for weeks in the garden.

Celosia

Feathery plumes or ruffled cockscomb types of celosia both go well with dahlias, providing contrasting textures, yet complementary colors. These easy-to-grow plants can be tucked in around dahlias, in containers or in flower beds. The cockscomb types look stunning in a vase with dahlias or by themselves.

Coleus

Traditionally, coleus was a shade-only plant, but newer varieties do fine in full sunshine. Look for a named variety rated for sun, or plant smaller shade-loving coleus later in the summer, and tuck them up tight to the dahlias, where their foliage can shelter them. Large-leaved, tall coleus are stunning on their own, but work particularly well at showing off dahlia blooms. 

Cosmos

A hedge of delicate green foliage loaded with white, pink, and wine-colored cosmos blooms makes an excellent backdrop for dahlias. Since most dahlias have darker green foliage, you’ll get the contrast of dark vs. light green in the foliage, and depending on the variety, simple vs. complex blooms.

Gladiolas

These summer-flowering bulbs produce elegant, tall spikes of flowers that contrast well with the more traditional bloom shapes of dahlias. Gladiolas like the same soil and sunlight as dahlias, and are available in so many shades that matching a color palette is easy if you desire. As a bonus, you can dig them both up at the same time in autumn and plant them together again in spring.

Ornamental Grasses

The arching stems and feathery plumes of ornamental grasses make a fantastic partner to the dense flower power of dahlias in late summer. Plant them in clumps behind or at the edges of a group of dahlias for a stunning early autumn display. Choose grasses with tall, arching stems to set off the upright dahlia form.

Petunias

Petunias are a favorite for providing color all season, and buying young plants to transplant into the garden gives them an even better head start. Mounding types like Wave petunias work well in the front of a dahlia bed to provide blooms while you wait for the dahlias. 

Pincushion Flower

These flowers like the same loose, well-drained soil and sunshine that dahlias thrive in, and will start blooming in early summer, continuing through to the frost. The blue shades of pincushion flower, also known as scabiosa, provide shades not found in dahlias (sadly, there are no true blue dahlias), and they work well as a front border or edge to a bed with dahlias.

Snapdragons

Snapdragons interplanted among the dahlias are a good way to add some color while you wait for the dahlias to flower. Snaps can be transplanted even before your last frost in spring, and will be flowering above the dahlia foliage by midsummer, if not before. When the larger dahlias are in bloom, the snapdragons will be fading a bit, and can be trimmed back if needed. 

Sunflowers

Sunflowers in the 2-3 foot range work well in front of larger dahlias. Taller 5-6 foot sunflowers will grow above the dahlia blooms and foliage, creating a layered effect. Many sunflower varieties bloom as soon as 50-60 days after sowing, providing a big early-season boost of color. 

Succession-plant sunflowers every ten days to have a continuous display, or direct-sow them a month after the dahlias were planted so they bloom at the same time. 

Zinnias

Tall, double-bloomed varieties of zinnias rival dahlias for their flower power and complexity of shape and form. They start easily from seed and are a great cut-and-come-again flower to add to dahlia bouquets.

More compact varieties, such as the Profusion Orange zinnias shown here, wor well in front of taller dahlias.