Lightly water so that soil is just damp, and continue to water lightly keeping the soil damp during sprouting. Sprouting should occur within a 7 to 10 day period. Do not over water. Keep in mind that unlike vegetable seed, dahlia seed will not all sprout the same day, germination will occur over several days.
After the young seedlings have reached a height of approximately 3 inches, they will be ready to separate and transplant into small "plugs" or pots. These containers should be filled with a potting soil and sand mix, approximately 2/3 potting soil and 1/3 sand. After potting up the seedlings, water enough to keep the soil dampened while they take root.
Continue to water and keep the soil damp as the plants grow. The seedlings will stay in these containers and continue to grow for about 4 to 5 weeks before they are ready for transplanting outside. Before you transplant outside, it is recommended that you harden off the young seedling first. They should be moved into a cold frame or the trays can be set outside during the day and brought in at night for a period of about 7 to 10 days.
This will help condition the young seedlings and they will and they will go through less shock when transplanted. Pick a sunny location that has well drained soil to transplant to. After transplanting your dahlias into your beds, be sure to keep them watered until the roots are established. (Approximate time 1-2 weeks) Please refer to the regular growing instructions for continued care for your dahlias.
These annual plants can be grown in zones 3-10.