Growing sunflower in zone 4b

In USDA zone 4b, the typical last spring frost is May 8 and the first fall frost is October 1. Here is when to plant sunflower against those dates.

USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service / Oregon State University PRISM Group. NOAA National Centers for Environmental Information, U.S. Climate Normals 1991-2020. Planting windows for sunflower from University of Minnesota Extension. Zone dates are medians; local conditions vary.