Dahlias are easy to grow and form a beautiful ground cover with many blooms. When growing your dahlias from seeds, expect a wide range of bloom colors from your mature plants. Dahlias like lots of sun and well-drained soil. Too little sun can cause them to grow tall and lanky and put on fewer blooms. Water your dahlias sparingly; they like damp soil but too much water can cause root damage.
Fill a growing tray half full of a commercial potting mix and lightly sprinkle with water until the soil is just damp.
Sprinkle dahlia seeds over the surface of the damp potting mix and then lightly cover with a thin layer of additional potting soil. Sprinkle with water again until the surface of the potting soil is damp, but not too wet.
Place the tray in location where it will stay warm--approximately 70 degrees Fahrenheit--and get plenty of indirect sunlight. Do not place the tray in direct sun. Keep the soil lightly moistened at all times. Look for sprouting to begin within seven to 10 days, but do not expect all seeds to sprout on the same day.
Fill individual growing pots with a mixture of two-thirds potting soil and one-third sand.
Dig up and transplant your dahlia sprouts carefully when they are approximately 3 inches tall. Keep the soil in the growing pots damp but not wet, and allow your sprouts to continue growing indoors in their pots for four weeks.
Harden off plants by taking them outdoors during the day and placing them in a sunny location and returning them indoors at night. Do this for seven days.
Loosen the soil in a sunny location of your garden and mix in approximately 1/3 cup organic fertilizer and 1 cup of bone meal for every square yard of soil. Cover the root ball of your dahlias with this garden soil and then water lightly until the soil is damp but not too wet. Keep the soil damp for at least 10 days until your Dahlias have established themselves.