About Dahlias
If you want loads of colorful flowers for weeks, and sometimes months, include dahlias in your flower garden. Here are the top four reasons gardeners love dahlias.
- They have a long flowering period. Unlike some flowers that bloom for a few weeks and are done, dahlias produce colorful flowers for weeks, from summer to frost.
- They’re great as cut flowers. Dahlia plants produce plenty of flowers for vases and bouquets—and the flowers easily last in vases for 7-10 days.
- They’re easy to grow in well-drained soil and sunny spots. Plant dahlia tubers in the spring—and enjoy the summer flower show.
- They come in a variety of colors and shapes, including ball, cactus, dinnerplate, decorative and karma. This makes them easy to fit into almost any color palette and style in the garden.
Below are some expert tips on how to grow dahlias that are sure to impress.
When to Plant Dahlias
Dahlias are tender perennials grown from tubers and planted in the spring. Because dahlias don’t grow well in cold soil, the key to growing vibrant, healthy dahlias is to plant them in late spring after soil temperatures reach 60 degrees F. A good rule of thumb is to wait until after your area’s last spring frost date. Because this may be in late May in many of the northern regions of the country, some gardeners plant dahlia tubers in pots in April or May (about 4-6 weeks before their last spring frost date) and then transplant dahlias to the garden after the danger of frost has passed. By doing this, you’ll enjoy dahlia flowers earlier in the summer.
Where to Plant Dahlias
When selecting places to plant your dahlia tubers, choose areas that have well-drained soil and plenty of direct sunlight (6 hours or more daily).
Starting Dahlias Indoors
For best results, select a container with at least a 12-inch diameter and with drainage holes at the bottom. Plant the tubers in potting soil or mix. The tubers should be covered with about 1 ½-inches of soil and watered well. Place the containers in a warm place where they’ll receive plenty of sunlight. The dahlias can be grown in containers or the plants can be transplanted outdoors once danger of frost has passed.
Planting Dahlias Outdoors
Here’s how to plant dahlia tubers outdoors. First, note your varieties height and space requirements, as some varieties can grow quite tall and wide. The soil for dahlias should be well drained and rich in organic matter. Dig a large planting hole that is at least twice as deep as the length of the dahlia tuber. Add dahlia fertilizer (Van Bourgondien 100% Natural Bulb Food is recommended) to the bottom of each hole. While the dahlia planting depth varies depending on the tuber size, the tuber should be covered with about 1 ½ inches of soil. Water well. After the dahlia sprouts appear above ground, water deeply to encourage strong roots. While the shorter border dahlias don’t need to be staked, other dahlias should be staked or caged.
Dahlia Care and Maintenance
While dahlias are low maintenance and easy to grow, they perform best with regular watering and staking. If your area does not receive at least an inch of rainfall weekly, water deeply once a week. Mulching can also help retain moisture. If planted in rich, organic soil and fertilized at planting, dahlias should not require additional fertilizer. Pinching and disbudding dahlias results in later, larger flowers. Staking or caging should be done when the plants are small. When staking, take care not to puncture or nick the roots.
Pinching Dahlias
Though dahlias will grow just fine on their own, pinching results in a stronger, bushier plant with more flowers. Pinch your dahlia plant when it’s 12–16 inches tall and has at least four sets of leaves on the center stalk. Locate the upper-most dahlia sprout on the main stem and remove it with your fingers or a pair of scissors. Take care not to damage the stem or nearby leaves.
If you want the largest flowers possible, do not pinch. Instead, remove auxiliary shoots. This allows the main flower to blossom to its fullest potential.
Deadheading Dahlias
We suggest removing spent flowers weekly. Deadheading encourages your dahlias to put their energies into producing more flowers, thereby promoting an extended display of form and color in the garden.
Dahlia Flower Care
Dahlias make excellent cut flowers. For cut flowers, pick flowers that are nearly or fully open because the buds usually will not open once they’re cut. Harvest early in the morning or late in the afternoon. Strip off all leaves that will be below the water line in your vase. Floral preservatives stimulate the flowers to open, extend the vase life and keep the water in the vase clean.
More Dahlia Growing Tips and Tricks
Slugs and snails may be a problem for some dahlia growers. Begin practicing slug control about two weeks after planting. Because dahlias attract pollinators, our experts prefer organic methods. A few tricks they use are:
- Spread coffee grounds around the plant.
- Place a glass jar or container into the ground so the rim is at soil level and fill with beer.
- Use organic slug pellets.
To control mites and earwigs, use a horticultural oil. The best way to avoid thrips is to remove weeds and grass around the dahlias. Spraying dahlias with a garden hose can reduce aphids.
Powdery mildew may show up in the fall. To prevent it, spray the plants with a mixture of baking soda (1/4 teaspoon) and water (1 quart).
While dahlias are not “deer proof,” they aren’t deer’s first choice of forage.
Storing Dahlia Tubers
When frost blackens the dahlia foliage in fall, cut your dahlias back to the ground. Then carefully lift each clump of tubers. Put the clumps in a container filled with perlite or brown peat. Space the tubers so that none are touching. Store the containers off the floor in an area with temperatures of 40–45°F. Replant in the spring.
More information about growing dahlias can also be found in K. van Bourgondien’s growing guide. If you’d like to try your hand at growing dahlias, browse our wide selection of dahlia bulbs for sale today!