Gardening in Zone 5 requires patience and optimism due to long winters. Dahlias, in particular, need extra care as they do not tolerate cold well.
The safe date for planting dahlias in Zone 5 is typically May 14. However, due to variability in weather, it's safer to plant around June 1st.
Start dahlia growth in pots in late April. Place tubers with their 'eyes' facing up in containers filled halfway with potting mix.
Dahlias can also be started from seeds in mid-April. Use seed trays filled with a seed starting mix and place in a consistently warm location.
In late May, begin the process of 'hardening off' by gradually exposing the dahlias to outdoor conditions before permanent planting.
Prepare your garden beds and plant your dahlias, ensuring they get at least 6 hours of direct sunlight and are not exposed to high winds.
Protect your dahlias from rogue frosts by tenting young growth with a blanket or tarp, or using severed water bottles or milk jugs as mini greenhouses.