Plant Sunflowers in Zone 4a

Seed-starting, transplant & harvest dates for USDA Zone 4a

Direct sow

May 17

Harvest (~80d)

Aug 5

Zone 4a averages 135 frost-free days, running from a last spring frost around May 10 to a first fall frost around September 22. Sunflowers needs roughly 80 days from planting out to first harvest, so it uses about 59 percent of that window. Sunflowers is a half-hardy crop, which is what decides where in the window it belongs.

Sunflowers resents transplanting and hates cold soil, so direct sow around May 17, after the Zone 4a last frost has passed and the soil has warmed.

Fall planting: sunflowers in Zone 4a

Sunflowers has no useful fall window in Zone 4a. Sunflowers need a long run of warm, long days and will not finish from a late-summer sowing outside frost-free zones.

Sunflowers need a long run of warm, long days and will not finish from a late-summer sowing outside frost-free zones.

Fall dates are counted backward from the Zone 4a average first frost, not forward from a sowing date. See the fall planting calendar by zone for the full method.

Spring vs fall sunflowers in Zone 4a

Planting	Sow or start	In the ground	Harvest
Spring	May 17	May 17	Aug 5
Fall	—	—	—

Last spring frost

May 10

First fall frost

Sep 22

Growing season

135 days

Sunflowers in nearby zones

Sunflowers in Zone 3b (colder) Sunflowers in Zone 4b (warmer) Full Sunflowers grow guide Zone 4a planting calendar

Other crops in Zone 4a

Tomatoes in Zone 4a Peppers in Zone 4a Cucumbers in Zone 4a Lettuce in Zone 4a Zucchini in Zone 4a Carrots in Zone 4a Beans (bush) in Zone 4a Peas in Zone 4a Broccoli in Zone 4a Spinach in Zone 4a Kale in Zone 4a Onions in Zone 4a Garlic in Zone 4a Potatoes in Zone 4a Squash (winter) in Zone 4a Corn in Zone 4a Radishes in Zone 4a Beets in Zone 4a Eggplant in Zone 4a Basil in Zone 4a Cilantro in Zone 4a Parsley in Zone 4a Pumpkins in Zone 4a

Frequently asked questions

When should I start sunflowers in Zone 4a?

Direct sow outdoors around May 17.

Can I direct sow sunflowers in Zone 4a?

Yes, direct sow around May 17.

Can I plant sunflowers in the fall in Zone 4a?