Most dahlias grown in the garden are hybrids that don’t breed true from seeds. If you plan to collect seeds from your own plants, expect surprises. Seeds purchased in packets are usually bedding annuals. These dahlias don’t grow as tall as perennials grown from tubers, and they don’t have large, showy blossoms, but they look great massed in borders.
Start dahlia seeds indoors 8 to 10 weeks before transplanting outdoors. Transplant outdoors 4 weeks after the last frost or when the soil and air are consistently warm. Dahlias need full sun and a deep, loose soil.
Difficulty: Moderately Easy
Fill the containers with starting medium to 1 inch from the top.
Place the seeds in the center of the pots and cover with about a half inch of soil.
Water the pots so that the soil is thoroughly moist. Discard any water that drains through.
Cover the pots with plastic wrap and set them in a warm place out of direct sunlight.
Remove the plastic wrap when the seeds germinate. Germination may take about a week.
Move the seedlings to a sunny window or use artificial lighting. Dahlia seedlings need a lot of light, so a south-facing window is best.
Monitor the soil moisture and add water as necessary. The soil should be moist but not soggy.
Scrub containers thoroughly, especially if they have already been used to start plants.
A fresh, unopened bag of starting medium is considered sterile. Never reuse starting medium.