Intro: Dahlia flowers do best in plant containers that are at least 1 by 1 foot, and low-growing and dwarf dahlia varieties are best for container gardening. There are so many dahlia flower varieties that every gardener can find something for their garden. These flowers come in every color imaginable for a flower except for blue. A blue dahlia flower has never been produced, even after the Caledonia Horticultural Society of Edinburgh offered a cash prize for the first person to grow a blue dahlia in 1846!
Scientific Name: Dahlia species
Plant Type: Tuberous perennial flowers native to Mexico and Central America
Light: Full sun
Zone: Tubers are hardy to Zone 8. If you dig up the tubers in summer and can provide 8 hours of full sun, dahlia flowers can be grown in any zone.
Fertilizer: Fertilize with a low-nitrogen fertilizer once a month (not water-soluble fertilizers). Don’t overfeed and avoid high-nitrogen fertilizers.
Pests and Diseases: Watch for snails and slugs, spider mites, aphids, earwigs and cucumber beetles. Powdery white mildew is common in the fall. Also watch for mold, wilt and viruses that could affect your dahlias.
Propagation: Propagate dahlias by dividing tubers. Plant dahlia tubers (with the eyes facing up) 6 inches deep (with the eyes 2 inches under the soil surface) and water them well right away. The best time to plant your dahlia flowers is in May. If you want to grow dahlias from seed, just remember that the seeds may not stay true to the parent – meaning that you may get different bloom colors and shapes than the parent plant. Start seeds indoors. Gently press the seeds into the potting soil and keep the soil moist until the dahlia seeds germinate within a week to 10 days. Once the dahlia seedlings reach 3 inches tall, put each one you want to use in its own plant container. In about a month, harden the seedlings off outside by keeping them outdoors during the day and bringing them in during the cool nights. Do this for about a week until the dahlias are ready to spend all their time outdoors in the garden.
Misc. Info: If you are growing a tall dahlia variety that grows to more than 3 feet, you will need to provide stakes or some other type of support. If you live in a colder climate in a Zone below Zone 8, you will have to overwinter your dahlia tubers inside. Dig up your dahlia tubers about two weeks after the first frost has killed the tops of the plants. Wash the dirt off the dahlia tubers, let them air dry for about a day and store them in a cool, dry area wrapped in paper. Don’t store the dahlia tubers in plastic bags. Check them throughout the winter to make sure they haven’t shriveled up or rotted away.
Cut dahlia flowers in a cool morning. To make your dahlia flower blooms last for about five days, rinse the cut stems in very hot water and allow them to cool. Cutting dahlia blooms will promote new blooms on the plant.
The dahlia is the national flower of Mexico and its tubers are often eaten in traditional Oaxacan cuisine.