How to grow tuberous begonia

When to plant tuberous begonia

Start tuberous begonias indoors in late winter, then move them outdoors once the weather has settled, the soil is warm, and all danger of frost is past (University of Minnesota: usually late May or early June in Minnesota). In cold climates the tubers are dug and stored dry over winter; left in the ground they would be killed.

Tuberous Begonia is timed by season rather than your frost dates, so the planting calendar does not generate ZIP-specific dates for it. Check the cited sources below to fine-tune for your area.