When to Plant Sunflower in Zone 4
Helianthus annuus
Last updated: Apr 29, 2026 · Sources: USDA, NOAA, Cooperative ExtensionAction Plan
Plant Sunflower in Zone 4
- Direct sow: May 24 — after last frost (May 10)
- First harvest: Aug 12 (70–100 days after planting)
⚠️ Don't plant before last frost (May 10) — cold snaps kill young transplants.
Last frost
May 10
First frost
Sep 25
Growing season
138 days
Quick Facts
Sunlight
☀️ Full Sun
Water Needs
💧 Low
Spacing
24 inches apart
Planting Depth
1.0 inch
Min Soil Temp
55°F
Germination
7–14 days
Days to Maturity
70–100 days
Frost Tolerance
No frost tolerance
Soil pH
6.0–7.5
Difficulty
Easy
What you'll need — Zone 4
🛒 Sunflower — Seeds & Supplies
- 🌱 Giant Sunflower Seeds
- 🌱 Sunflower Bird Feeder
- 🌱 Tall Plant Stakes
Search for these at your local garden center or nursery.
Growing Tips
- Direct sow after last frost — sunflowers dislike transplanting.
- Plant in groups for better cross-pollination and seed production.
- Deadhead spent blooms to encourage branching varieties to continue flowering.
- Leave seed heads on the stalk in fall for birds.
- Thin to 12–24 inches apart — crowded sunflowers produce smaller heads.
Common Mistakes
- Transplanting — sunflowers have taproots that don't survive disturbance.
- Planting too deep — seeds only need 1 inch depth.
- Growing near potatoes — sunflowers produce allelopathic compounds.
- Not staking tall varieties — heavy heads snap in wind without support.
Companion Planting
Companion planting improves growth, deters pests, and makes better use of garden space.
✓ Good Companions
✗ Avoid Nearby
Potato
Sunflower Schedule — All Zones
| Zone | Start Indoors | Transplant | Direct Sow | Harvest Start | Harvest End |
|---|---|---|---|---|---|
| Zone 2 | — | — | Jun 8 | Aug 27 | Sep 2 |
| Zone 3 | — | — | May 29 | Aug 17 | Sep 12 |
| Zone 4 | — | — | May 24 | Aug 12 | Sep 22 |
| Zone 5 | — | — | May 14 | Aug 2 | Oct 1 |
| Zone 6 | — | — | Apr 29 | Jul 18 | Sep 16 |
| Zone 7 | — | — | Apr 19 | Jul 8 | Sep 6 |
| Zone 8 | — | — | Apr 3 | Jun 22 | Aug 21 |
| Zone 9 | — | — | Mar 14 | Jun 2 | Aug 1 |
| Zone 10 | — | — | Feb 24 | May 15 | Jul 14 |
| Zone 11 | — | — | Jan 29 | Apr 19 | Jun 18 |
Other Zones for Sunflower
Zone 2 · Zone 3 · Zone 5 · Zone 6 · Zone 7 · Zone 8 · Zone 9 · Zone 10 · Zone 11
📚 Data Sources
Frost dates: NOAA Climate Normals 1991–2020, National Centers for Environmental Information.Hardiness zones: USDA Plant Hardiness Zone Map, Agricultural Research Service.
Growing requirements: Cooperative Extension Services — NC State, Penn State, University of Florida IFAS.
Companion planting: Cornell University Cooperative Extension.
Data compiled from public agricultural sources. Always verify with your local extension office for micro-climate adjustments.