DibbleWhen to plant sunflowers in Zone 3
In Zone 3, the last spring frost usually passes around May 15 and the first fall frost arrives around September 15, leaving about 123 frost-free days. The windows below are computed from those frost dates, with the same math the Dibble app uses.
Short, cool season. Start most warm crops indoors and protect from late frosts.
Planting windows for sunflowers in Zone 3
| Task | Window |
|---|---|
| Direct sow | May 15 to May 29 |
| Estimated harvest | Aug 3 to Aug 24 |
The harvest estimate counts 80 days to maturity, then a picking window of about 21 days. These windows use typical frost dates for Zone 3; Dibble pins them to your exact ZIP code.
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Sunflower in a Zone 3 season
Zone 3 gives about 123 frost-free days. Sunflower needs roughly 80 days from sowing. That leaves about 43 days of slack, enough for one full crop with a little room for a cold spring.
Sowing every 14 days, Zone 3 has room for about 4 plantings.
How to grow sunflowers
Sow sunflowers around your last frost date. Stagger plantings every couple of weeks for blooms all summer.
Companion plants
Good neighbors for Sunflower:
Better kept apart:
Sunflower in other zones
Not in Zone 3? Pick your zone for the same dated windows.
Keep exploring
Sunflower: the full growing guide · The Zone 3 planting calendar · Every crop and zone
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Dates are estimates based on typical frost dates for the zone. Your yard has its own microclimate, so use them as a starting point and adjust as you learn your space.