When to plant sunflower in zone 3b — planting calendar

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Showing USDA Zone 3B

Growing SeasonZone 3b

Last frost ~May 25First frost ~Sep 15Today

Start indoorsTransplant / sowHarvestFrost risk

MAYJUNJULAUG

Sow May 25 · First harvest Jul 24 · Wrap by Aug 21

Last spring frostMay 25

Direct sowMay 25

First harvestJul 24

Last harvestAug 21

First fall frostSep 15

Why these dates work in zone 3b

Zone 3b's last spring frost averages May 25 and first fall frost Sep 15 — about 113 frost-free days. Sunflower is frost-sensitive, so the around last frost timing builds in a safety margin against a late cold snap — setting plants out too early risks losing them to frost.

Common questions

How long does sunflower take to grow in zone 3b?

Sunflower matures in about 60–100 days from sowing. In zone 3b that means sowing around May 25 and first picking around Jul 24.

Will sunflower survive frost in zone 3b?

No — sunflower is frost-sensitive. In zone 3b, wait until after the last frost (around May 25) to plant, and harvest before the first fall frost (around Sep 15).

For soil, spacing, pests and companion planting, see the full sunflower growing guide →