Dahlias are brightly colored flowers that bloom in late summer and early fall after others have stopped blooming. Their size ranges from a small dwarf size to giant dahlias, and they come in a wide variety of colors. You can find them in any color but blue and black. They add color to any garden and make great cut flowers. Dahlias should be planted in late spring from mid-April to May in most places. In very hot climates, you can plant them outdoors early, as soon as temperatures reach 60 degrees F. However, if you want, you can start from seed and plant your dahlias inside.
Spread potting soil across the bottom of a flat tray with low edges.
Sprinkle the flower seeds over the top of the soil, and then cover them with another thin layer of potting soil.
Water until the soil is damp. Make sure the soil stays damp the whole time the dahlias are sprouting, about seven to 10 days.
Separate the seedlings when they are 3 inches tall. Transplant them into small pots, filled with a mixture of 2/3 potting soil and 1/3 sand.
Water enough to keep the soil damp as the seedlings establish roots and the dahlias grow. They will grow in these pots for four or five weeks.
Move the pots outside during the day and back in at night for about a week before you transplant them outside. This will help prepare the young to be planted outside and reduce shock.
Transplant the seedlings to your bed outdoors. They will need about eight hours of sunlight daily and well-drained soil.