Dahlias are annual flowers in zones 3 to 11. They are colorful, sturdy plants in every color of the rainbow except blue. Growing dahlias from seeds can be done indoors about 8 weeks before the last frost, or outdoors in the garden in areas that have a longer growing season.
Planting Dahlia Seeds
To start seeds indoors, fill a potting tray with potting mix. Plant the seeds about inches deep. Cover with soil and water gently. The soil should not be soggy, just moist.
Keep the indoor seeds in a brightly lit area that is warm, above 60 degrees. Germination usually takes about 7 to 10 days.
Water the seeds daily, just so the soil remains moist. Once the seedlings reach 3 or 4 inches, they can be transferred to individual pots. Once they reach 12 inches, they should be ready to be planted outdoors, weather permitting.
If growing seeds outdoors, choose a site that is fertile, well-drained and in full sun (afternoon shade in warmer climates). Space the seeds in the soil 12 inches apart and about 2 to 3 inches deep. Water gently and daily until established.
Seedlings started indoors can be moved outdoors to the garden in the spring, after the last frost. Once they're established, remove spent flowers to encourage more blooms.