When should I start dahlias indoors?
For earlier bloom, start dahlia tubers indoors in early April. Fill an 8-inch-diameter pot about one-half full with a commercial potting mix, place a tuber horizontally on the potting mix surface, then cover with an additional 1 or 2 inches of potting soil. Water thoroughly. When growth emerges, place the dahlias in a sunny window or under artificial lighting.
Dahlias can also be grown from seeds. Sow seeds indoors 10 to 12 weeks before the date of the average last spring frost.
Plant dahlias outdoors after the danger of frost is past. Before planting, harden or acclimate the dahlias to outdoor conditions for several days. Initially place the dahlias in a shady, protected location. Then gradually expose the plants to longer periods of sun.