Starting Dahlias from Seeds

• Growing dahlias from seeds isn’t any harder than growing most other annuals from seeds. However, there are a few things to keep in mind.

• The flowers of dahlia seedlings rarely look like their seed parents. Due to the octoploid genome (8 sets of chromosomes), countless combinations of different genetic traits can occur in seedlings.

• Some of the dominant traits that tend to prevail in seedlings are open disc centers, low petal count, small blooms, tall plants, poor form, weak stems, downward facing blooms, or a single set of petals. Thus, most seed dahlias don’t look like the flashy big show dahlias most of us admire. But seed plants are usually much more vigorous and healthier than plants grown from tubers. They will do great in a garden border and are a fall favorite of many pollinators. Most seed dahlias will also make tubers that can be overwintered.

• Desirable traits such as high petal counts, strong stems, good tubers, large blooms, and closed centers are far less common. It’s estimated that only 1 out of 1,000 seedlings has the right combination of desirable traits to become a show flower variety.

• Seed germination typically takes between 3 days to 1 week and up to 2 weeks. However, due to the complicated genetics, even fat looking seeds might not sprout. Germination rates can sometimes be very low. Seeds can be pre-sprouted between wet paper towels in plastic bags to save space. Paper towels need to be checked daily and sprouted seeds have to be transplanted immediately and very carefully into pots with soilless growing medium.

• Alternatively, sow seeds densely into soilless or seed starter mix and prick them out into larger pots as they germinate.

• Dahlia seeds are very cold sensitive and should be started indoors 4 to 8 weeks before planting outside. Keep seedling trays or wet paper towels at a temperature of 70°F or higher.

• Plant seedlings outside in late May. They should be well rooted and have at least 3 sets of true leaves.

• Space plants 12 inches apart. If you want to increase the number of seedlings to evaluate, plant them 4 inches apart and then cull seedlings with undesirable traits as they bloom.

• You can save your own seeds or buy seeds. However, many fully double show dahlia varieties make no or only few seeds. Therefore, high quality seeds from experienced dahlia hybridizers may cost $.50 to $2 for each seed.

• Seeing a completely novel dahlia bloom, one you cultivated from seed, is a joy beyond measure.

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