Planting Dahlia
Dahlia is a warm season flower in the Asteraceae family. Getting the timing right is the difference between a strong stand and a disappointing one, so the windows below are given relative to your own last spring frost and first fall frost rather than a generic calendar date. Look up your local frost dates and count back or forward from there.
Transplant young plants outdoors 0–2 weeks after your last frost, once the danger of frost has passed.
Spacing and Planting Depth
Give Dahlia room to mature. The figures below come from verified extension and seed-supplier data for typical varieties.
| Spacing in row | 18 inches |
|---|---|
| Row spacing | 24 inches |
| Plants per sq ft | 0.33 |
| Planting depth | 4 inches |
| Sun requirement | Full sun |
Days to Maturity
Dahlia reaches maturity in 90–120 days from sowing.
Dahlia is ready to harvest after about 105 days. Harvest before the first fall frost, which will end the plant's productive season.
Conditions and Care
As a warm-season flower, Dahlia needs warm soil and settled weather to thrive, and is set back or killed by frost. It is frost tender, so wait until all danger of frost has passed before planting out and harvest before the first fall frost.
Dahlia needs full sun — give it at least six hours of direct light a day for the best growth and flavor. Sow seed about 4 inches deep, then keep the soil evenly moist until seedlings establish.
Dahlia belongs to the Asteraceae family; rotating where you grow members of this family each year helps limit the build-up of soil-borne pests and disease. Dahlia is generally grown as a single planting each season rather than succession sown.
Growing Notes
Grown from tubers; lift before hard frost in cold zones.