Did you know dahlias can be grown from seed? Many gardeners are only familiar with growing dahlias from tubers. Still, growing dahlias from seed is how new varieties are first created. Then they are sold commercially as tubers to produce true-to-type varieties for consumers. Home gardeners can do this too! This year in my flower garden, I grew several dahlia forms (different flower shapes or sizes). I grew varieties ranging from open-centered to pompon and anemone flowered blooms and relied on open pollination from the bees to do the breeding work for me. Once the blooms dry up, and the seed heads are mature, I will collect the seeds and wait until spring to plant them and see what new and exciting varieties come up.
Open centered Dahlia’s grown from seed. Dahlias are available in a wide spectrum of colors, growth habits, flower size and shape.
Mary Vargo, ©2022, Clemson Extension
Dahlia
Dahlias are in the Asteraceae family, one of the most prominent plant families globally, with species distributed across the globe. The plants in this family are termed composites because of the anatomy of their bloom, which is, botanically speaking, a composite of individual flowers called florets.
Dahlia flowers have two types of florets: disc florets (the center of the flower) and ray florets (also called petals). While the ray florets draw pollinators to the flowers with their bright colors, they are usually infertile. In contrast, the disc florets are typically the most fertile part of the flower and, if pollinated, can produce seed.
Ray (petals) and disc florets (center of flower) on an open-centered form of dahlia.
Mary Vargo, ©2022, Clemson Extension
Open Pollination
My method of collecting seeds from my dahlias this year was a simple strategy of open pollination, allowing the local bees to pollinate the blooms available to them.
The form of a dahlia bloom can influence the number of pollinators that will visit due to easy access or lack of access to the center of the disc florets where the pollen is. Open-centered dahlias give pollinators easy access to their disc florets and always result in viable seeds for collecting. Other forms of dahlias, such as double-flowered forms, aren’t as appealing to pollinators because their disc centers lack visibility, so the bees usually end up visiting the open-centered varieties instead.
Open-centered dahlias give pollinators easy access to their disc florets. Mary Vargo, ©2022, Clemson Extension
Double flowered forms are one of several forms that pollinators have a difficult time finding the disc florets and pollen. Mary Vargo, ©2022, Clemson Extension
While most of the bees were indeed attracted to the open-centered varieties rather than the double blooming varieties in my garden, because of this, the pollen the bees will be spreading will tend to produce seeds with plants that have open-centered forms. So, I know what flower form to generally expect from these seeds when I grow them out to flower next year.
Collecting and Storing Seeds
Collecting seeds from dahlias is typically done in the fall once the plants bloom and seed heads have entirely dried up. If pollination has occurred, you will find tiny, dark bottle-necked-shaped seeds within the seed head that can be stored immediately. Seeds can also be collected from seed heads that haven’t completely dried up, but the flower has been pollinated, and if the seed head is firm when given a gentle squeeze, check for the presence of mature seed that can be dried out, and then stored in a dry, dark, and cool place.
Dried seed head with viable seeds.
Mary Vargo, ©2022, Clemson Extension
Dried seed head with viable seeds.
Mary Vargo, ©2022, Clemson Extension
Mature seed head with viable seeds.
Mary Vargo, ©2022, Clemson Extension
Seeds can also be collected from seed heads that can be dried out, and then stored in a dry, dark, and cool place.
Mary Vargo, ©2022, Clemson Extension
Germination and Transplants
In the spring, dahlia seeds can be sown indoors 4-6 weeks before the last frost. Plant dahlia seeds ¼” deep in seed starting medium and keep evenly moist until germination occurs. Once seedlings have 1-2 sets of true leaves, they can be transplanted outdoors in a well-drained location and full sun.
Dahlia seedlings ready for transplanting.
Mary Vargo, ©2022, Clemson Extension
Plants started by seed will produce tubers that can be dug up in the fall and stored to be planted again in the spring. Suppose you are particularly fond of one of the Dahlia seedling’s flower colors. In that case, habits and overall performance, the tubers harvested from this dahlia will produce the exact replicate of this hybrid, and you can enjoy it for years to come.
For more information on dahlias and other summer flowering bulbs, see HGIC 1156, Summer- and Fall-Flowering Bulbs.
