When to Plant Sunflower in Zone 4b

Helianthus annuus

Last updated: May 15, 2026 · Sources: USDA, NOAA, Cooperative Extension
Action Plan

Plant Sunflower in Zone 4b

  • Direct sow: May 24
  • First harvest: Aug 12 (70–100 days)
⚠️ Zone 4b last frost: May 3. Don't plant frost-sensitive crops before this date.
Last frost
May 3
First frost
Oct 2
Growing season
152 days
Zone 4b is the warmer half of Zone 4

Zone 4b has a last frost around May 3 and first frost around Oct 2, giving you approximately 152 growing days. This is about 2 weeks longer than Zone 4a. For more details see the Zone 4 complete guide.

Other Zones for Sunflower

Zone 2Zone 3Zone 4Zone 5Zone 6Zone 7Zone 8Zone 9Zone 10Zone 11
📚 Data Sources
Frost dates: NOAA Climate Normals 1991–2020, National Centers for Environmental Information.
Hardiness zones: USDA Plant Hardiness Zone Map, Agricultural Research Service.
Growing requirements: Cooperative Extension Services — NC State, Penn State, University of Florida IFAS.
Companion planting: Cornell University Cooperative Extension.
Data compiled from public agricultural sources. Always verify with your local extension office for micro-climate adjustments.