Dahlias can be started indoors in individual pots with damp peat moss and vermiculite. You must use caution when transplanting them outdoors. Plant dahlias outdoors after all danger of frost has passed. Choose a sunny site with well-drained, sandy soil. Dig a hole a little larger than the 2” you’ll need to plant the Dahlia. Amend soil with peat moss or compost. Replace about half the soil, then place tubers flat and cover with remaining soil. Space tubers 12-36" apart depending on variety. Water after planting and not again until shoots appear. Stake plants. As plants grow increase watering. Fertilize sparingly. Pinch and disbud dahlias for later and larger flowers. Buds tend to grow in threes; two-sided ones should carefully be pinched to develop the central bloom. This is especially important with border or pot plant dahlias. If the plants are not pinched back, they will not retain their low compact size.
In areas with winter freeze, carefully dig the tubers in fall after the frost kills the foliage. Cut the stalk approximately 6" above the tuber. Dahlias should be dried for only a couple of hours before storing in plastic-lined shallow boxes with a blanket of vermiculite or peat moss. Hardy in Zones 8-10.