Plant Sunflowers in Zone 4b

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

Direct sow

May 12

Harvest (~80d)

Jul 31

Zone 4b averages 146 frost-free days, running from a last spring frost around May 5 to a first fall frost around September 28. Sunflowers needs roughly 80 days from planting out to first harvest, so it uses about 55 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 12, after the Zone 4b last frost has passed and the soil has warmed.

Fall planting: sunflowers in Zone 4b

Sunflowers has no useful fall window in Zone 4b. 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 4b 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 4b

Planting	Sow or start	In the ground	Harvest
Spring	May 12	May 12	Jul 31
Fall	—	—	—

Last spring frost

May 5

First fall frost

Sep 28

Growing season

146 days

Sunflowers in nearby zones

Sunflowers in Zone 4a (colder) Sunflowers in Zone 5a (warmer) Full Sunflowers grow guide Zone 4b planting calendar

Other crops in Zone 4b

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

Frequently asked questions

When should I start sunflowers in Zone 4b?

Direct sow outdoors around May 12.

Can I direct sow sunflowers in Zone 4b?

Yes, direct sow around May 12.

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