Dahlia tubers should be planted after the danger of frost has passed and the soil has warmed to at least 60°F (around 15°C). This typically means planting outdoors in mid to late spring, usually from mid-April to late May depending on the climate zone. It is important to plant them in well-drained soil and a sunny location. For earlier starts, tubers can be planted indoors in pots in March or early April and then transplanted outside once the frost risk is gone. Key details:

• Plant tubers about 5-6 inches deep with the eye (growth bud) facing upward.
• Space them about 12-18 inches apart depending on variety.
• Avoid planting while the soil is cold or frosty to prevent rot.
• In colder regions, wait until late May or early June for outdoor planting.
• Tubers can be started indoors under cover to get a head start on growth before moving outside.

This timing ensures the plants grow vigorously and flower by summer, avoiding frost damage and reducing the risk of tuber rot from cold, wet soil.