When should I plant Sunflower in Zone 4a?

Start Sunflower seeds indoors around Apr 14. Transplant outdoors after May 12. Expect first harvest around Jul 16.

What is the last frost date for Zone 4a?

The average last spring frost date for Zone 4a is May 5. The first fall frost averages Oct 1, giving a 149-day growing season.

Can I grow Sunflower in Zone 4a?

Yes. Sunflower needs 90 days to harvest. Zone 4a has a 149-day growing season, which is sufficient. You can plant up to 4 successions.

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🌻 Growing Sunflower in Zone 4a

Zone 4a has cold winters and a moderate growing season. Timing is key for Sunflower in this zone. Last frost: May 5. First frost: Oct 1.

Planting Calendar

Indoor

Outdoor

Harvest

Apr 14Oct 1

Season: May 5 – Oct 1 (149 days) · Succession: plant every 2 weeks (up to 4x)

Zone4a

Last FrostMay 5

First FrostOct 1

Season Length149 days

Days to Harvest90

SunFull Sun

Frost ToleranceNone

Spacing1/sqft (12" apart)

When to Plant Sunflower in Zone 4a

Start Seeds Indoors: Apr 14

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

Transplant Outdoors: May 12

Transplant Sunflower seedlings outdoors after May 12. 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 16

First harvest approximately Jul 16 (~65 days from transplant). Continue harvesting until first frost (Oct 1).

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

Plan Your Sunflower Garden

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

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