When to plant sunflower in zone 4a — planting calendar

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Showing USDA Zone 4A

Growing SeasonZone 4a

Last frost ~May 20First frost ~Sep 20Today

Start indoorsTransplant / sowHarvestFrost risk

MAYJUNJULAUG

Sow May 20 · First harvest Jul 19 · Wrap by Aug 16

Last spring frostMay 20

Direct sowMay 20

First harvestJul 19

Last harvestAug 16

First fall frostSep 20

Why these dates work in zone 4a

Zone 4a's last spring frost averages May 20 and first fall frost Sep 20 — about 123 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 4a?

Sunflower matures in about 60–100 days from sowing. In zone 4a that means sowing around May 20 and first picking around Jul 19.

Will sunflower survive frost in zone 4a?

No — sunflower is frost-sensitive. In zone 4a, wait until after the last frost (around May 20) to plant, and harvest before the first fall frost (around Sep 20).

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