Dahlia – A Magnificent Perennial
The splendid dahlia becomes the centerpiece of the garden from midsummer well into the fall. Dahlia’s underground tubers are stored over winter, enabling them to return with an increasing number of blooms year after year.
The Empress’s Favorite
Dahlias come in over 50,000 different varieties, ranging from yellow, white, pink, red, to purple. They vary from neat little plants of 30 centimeters to towering giants of almost two meters. This diversity makes dahlias extremely easy to pair with other plants. We love intercropping dahlias with spring-flowering bulbs. When crocuses and daffodils fade, the lush leaves of dahlias take over, guiding the garden into summer.
Originally from the Mexican mountainous regions, where it is known as cocoxochitl, the name “dahlia” actually comes from the Swedish botanist Anders Dahl.
Dahlias were primarily brought to Europe as a food crop. Although their tubers are edible, they are not considered culinary delights. Instead, it was the incredibly beautiful flowers that took Europe by storm. Napoleon’s wife, Joséphine Bonaparte, was one of the enthusiasts. She refused to let anyone else take care of the dahlias in the Malmaison castle garden.
Planting Dahlia Tubers
- Pre-sprout Dahlia Tubers
Dahlias can be pre-cultivated in March-April for an extra early bloom. Place the tubers about 10 cm deep in a large pot with potting soil. Keep the pot warm and water very sparingly until the green shoots appear. Thereafter, dahlias prefer a bright but cool environment. After the last spring frost, move the dahlias outdoors. Let the plants acclimatize to the new climate. Place them in a sheltered spot for a few days and bring them in at night.
- Direct Planting of Dahlia Tubers
It’s also perfectly fine to directly plant dahlia tubers outdoors in a flower bed or in pots. This is done when the weather becomes milder in May or June. Protect them with a row cover or leaves during frosty nights.
Top Dahlias – and Take Cuttings!
Dahlias can be topped when they reach about 20 cm in height. This encourages the stems to branch out, resulting in dense and bushy plants. As a bonus, the clipped tops can be planted in soil, giving you even more dahlias. These cuttings may not have time to form tubers during the summer, but there’s a good chance they will bloom.
Caring for Dahlia
Dahlias thrive best in a sunny spot in a sheltered location. Surprisingly, dahlias are easy to grow – they happily bloom even in partial shade. Water regularly and provide nutrients until September.
If the dahlia dries out, it can be susceptible to powdery mildew, appearing as a white powder on the leaves. In such cases, try mixing two teaspoons of soap and two teaspoons of baking soda in a liter of water. Spray the solution on the leaves and repeat after rainfall.
Dahlias are gorgeously stunning in bouquets, so pick and enjoy them. Also, snip off faded flowers to stimulate new bud formation and prolong flowering.
Overwintering Dahlia Tubers
When frost approaches, it’s time to move the dahlia tubers to a dark, cool, but frost-free place. The ideal temperature is 4-6 degrees. If the dahlias are grown in pots, you can bring the entire pot indoors. Otherwise, gently dig up the tubers from the ground, cut off the stems, and let the tubers dry for a couple of days.
Then, let the dahlia tubers overwinter in a slightly moist-retentive material, such as a plastic bag filled with wood shavings or perlite, or a mix of pine needles and cones. Don’t forget to label the bag with the variety name. During winter, check on our tubers occasionally, remove any that have become soft, and spray some water if it seems too dry.
The tubers can be divided in autumn or spring before planting. Just ensure that each tuber has at least one “eye” (bud) from which the growth will emerge – for the next delightful season of blooming dahlias.
Author: Johanna Damm
Fact-checked by Erik Hoekstra
Last updated: 2023-10-20