When to plant sunflower in zone 4b — planting calendar

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Showing USDA Zone 4B

Growing SeasonZone 4b

Last frost ~May 15First frost ~Sep 25Today

Start indoorsTransplant / sowHarvestFrost risk

MAYJUNJULAUG

Sow May 15 · First harvest Jul 14 · Wrap by Aug 11

Last spring frostMay 15

Direct sowMay 15

First harvestJul 14

Last harvestAug 11

First fall frostSep 25

Why these dates work in zone 4b

Zone 4b's last spring frost averages May 15 and first fall frost Sep 25 — about 133 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 4b?

Sunflower matures in about 60–100 days from sowing. In zone 4b that means sowing around May 15 and first picking around Jul 14.

Will sunflower survive frost in zone 4b?

No — sunflower is frost-sensitive. In zone 4b, wait until after the last frost (around May 15) to plant, and harvest before the first fall frost (around Sep 25).

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