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🌻 Growing Sunflower in Zone 3b

Zone 3b has harsh winters and a short growing season. Start Sunflower early indoors to maximize your harvest window. Last frost: May 15. First frost: Sep 22.

Planting Calendar

Indoor

Outdoor

Harvest

Apr 24Sep 22

Season: May 15 – Sep 22 (130 days) · Succession: plant every 2 weeks (up to 2x)

Zone3b

Last FrostMay 15

First FrostSep 22

Season Length130 days

Days to Harvest90

SunFull Sun

Frost ToleranceNone

Spacing1/sqft (12" apart)

When to Plant Sunflower in Zone 3b

Start Seeds Indoors: Apr 24

Start Sunflower seeds indoors around Apr 24 (3 weeks before last frost). Optimal germination temperature: 75°F. Germinates in 7–14 days.

Transplant Outdoors: May 22

Transplant Sunflower seedlings outdoors after May 22. Wait until soil temperature reaches 55°F. Space plants at 1/sqft (12" apart). Harden off plants for a week before moving outside.

Harvest: Jul 26

First harvest approximately Jul 26 (~65 days from transplant). Continue harvesting until first frost (Sep 22).

Companion Planting

✅ Cucumbers✅ Squash ✅ Corn✅ Beans

❌ Potatoes

Sunflower in Other Zones

1a 1b 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a 10b 11a 11b 12a 12b 13a 13b

Frequently Asked Questions

When should I plant Sunflower in Zone 3b?

Start Sunflower seeds indoors around Apr 24. Transplant outdoors after May 22. Expect first harvest around Jul 26.

What is the last frost date for Zone 3b?

The average last spring frost date for Zone 3b is May 15. The first fall frost averages Sep 22, giving a 130-day growing season.

Can I grow Sunflower in Zone 3b?

Yes. Sunflower needs 90 days to harvest. Zone 3b has a 130-day growing season, which is sufficient. You can plant up to 2 successions.

What is the best month to plant Sunflower in Zone 3b?

The best time to start Sunflower in Zone 3b is Apr. Begin seeds indoors around Apr 24, then transplant outdoors after the last frost date of May 15.

What companion plants grow well with Sunflower?

Good companion plants for Sunflower include Cucumbers, Squash, Corn, Beans. Avoid planting Sunflower near Potatoes.

How long does Sunflower take to harvest?

Sunflower takes approximately 90 days from planting to harvest. In Zone 3b, expect your first harvest around Jul 26.

Plan Your Sunflower Garden

Track Sunflower from seed to harvest with personalized frost dates, watering recommendations, and companion planting visualization.

Start Free Sunflower Growing Guide