When to Plant Dahlias
Spectacular summer-to-fall bloomers producing dinner-plate-sized flowers in every color except blue. Grown from tubers planted after frost.
The Short Answer
How to Grow Dahlias
Dahlias are grown from tubers planted after frost, and the range of forms is staggering: dinnerplate varieties produce flowers up to 12 inches across, while pompon types are tight, perfect spheres under 2 inches. Stake tall varieties at planting time — installing stakes after the plant grows risks piercing the tuber. Pinch the center growing tip when plants reach 12 inches tall to encourage branching and more (but smaller) flowers. In zones 7 and colder, dig tubers after the first killing frost, divide, and store in barely-damp peat moss in a cool (40-50°F) location over winter.
Starting Seeds Indoors
Begin dahlias seeds indoors 4 weeks before your average last frost date. Seeds need soil temperatures of at least 60°F to germinate, which typically takes 7-14 days. Provide 12 hours of light per day using a south-facing window or grow lights.
Transplanting
Move seedlings outside 2 weeks after your last frost date, once soil temperatures reach 60°F. Harden off seedlings for 7 days before transplanting by gradually exposing them to outdoor conditions.
Growing Tips
Plant tubers horizontally, 6 inches deep. Stake tall varieties at planting time. Pinch center growing tip when 12 inches tall for bushier plants with more blooms. Dig tubers before frost for winter storage.
Companion Planting
Good companions:
Dahlias Planting Dates by State
Click your state for dahlias planting dates specific to your location:
Last reviewed: March 29, 2026