When to Plant Sunflower in USDA Zone 3a
Top priorities for Zone 3a gardeners in May
Your garden in Zone 3a is working on a schedule, even when you're not. Here's where you should be this May.
Want it on paper? Download your Zone 3a planting guide →Sunflowers are tall, cheerful annuals grown for their edible seeds and as pollinator magnets. They come in sizes from 2-foot dwarfs to 12-foot giants.
In Zone 3a, the average last spring frost is around May 15 and the first fall frost is around September 15, giving you a growing season of approximately 123 days.
Sunflower Planting Timeline — Zone 3a
Where Is USDA Zone 3a?
The map below highlights the states that contain Zone 3a. Click any state to see the Sunflower planting schedule for that location.
Sunflower Planting Calendar — Zone 3a
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 13 | Mar 13 – Mar 27 |
| Transplant Outdoors | June 5 | Jun 5 – Jun 19 |
| Direct Sow | May 29 | May 29 – Jun 19 |
| Harvest | August 14 | Aug 14 – Oct 2 |
Plant 1" deep · 18" apart · Rows 30" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Free Zone 3a Planting Calendar PDF
Know exactly when to plant every crop in your zone. Get a printable month-by-month calendar customized for Zone 3a with start dates, transplant windows, and harvest times.
Growing Conditions
Sun
Full Sun (6-8+ hours)
💧 Water
Low — drought tolerant
Days to Maturity
70–100 days
Soil pH
6 – 7.5
Zone Temperature Range
°F to °F average annual minimum
Growing Season
123 days (Zone average)
Planting Specifications
| Planting Depth | 1 inches |
| Plant Spacing | 18 inches apart |
| Row Spacing | 30 inches between rows |
Growing Tips for Sunflower in Zone
Zone has a short growing season (~123 days). Start Sunflower indoors early and use season-extension techniques like row covers and cold frames.
Direct sow after last frost. Stake tall varieties in windy areas. Harvest seed heads when the back turns brown and seeds are plump. Dry heads upside down.
Companion Planting
Good Companions
Avoid Planting Near
The Gardener's Encyclopedia to Companion Planting
The pairings that make vegetables, herbs, and flowers grow better — and the ones that quietly wreck a bed.
- Proven pairings for 200+ vegetables, herbs, flowers, and fruits
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Saving Sunflower Seeds
Recommended for Your Garden
Start seeds indoors with reusable cell trays and humidity domes.
Test your soil pH, nitrogen, phosphorus, and potassium levels before planting.
Keep your garden organized with durable, weather-resistant plant labels.
Related Plants
Sunflower in Other Zones
Sunflower by State
- Alabama
- Alaska
- Arizona
- Arkansas
- California
- Colorado
- Connecticut
- Delaware
- Florida
- Georgia
- Hawaii
- Idaho
- Illinois
- Indiana
- Iowa
- Kansas
- Kentucky
- Louisiana
- Maine
- Maryland
- Massachusetts
- Michigan
- Minnesota
- Mississippi
- Missouri
- Montana
- Nebraska
- Nevada
- New Hampshire
- New Jersey
- New Mexico
- New York
- North Carolina
- North Dakota
- Ohio
- Oklahoma
- Oregon
- Pennsylvania
- Rhode Island
- South Carolina
- South Dakota
- Tennessee
- Texas
- Utah
- Vermont
- Virginia
- Washington
- West Virginia
- Wisconsin
- Wyoming
Frequently Asked Questions
When should I plant Sunflower in Zone 3a?
In Zone 3a, plan your Sunflower planting around the average last frost date of May 15. Start seeds indoors around March 13. Direct sow outdoors around May 29. Transplant seedlings around June 5.
Can Sunflower grow in Zone 3a?
Yes, Sunflower can grow well in Zone 3a, hardy in USDA zones 2a through 11b. Zone 3a has a growing season of approximately 123 days, which is sufficient for Sunflower (70-100 days to maturity).
When can I harvest Sunflower in Zone 3a?
In Zone 3a, expect to harvest Sunflower from August 14 – October 2. Sunflower takes 70-100 days from planting to harvest.
What is the last frost date for Zone 3a?
The average last spring frost in Zone 3a is around May 15, and the first fall frost is around September 15. This gives a growing season of approximately 123 days. These are 50% probability dates — actual frost dates vary year to year.
What should I plant next to Sunflower?
Good companion plants for Sunflower include Corn, Cucumber, Squash Summer. These companions can help with pest control, pollination, and nutrient sharing.
Your Free Printable Garden Planner
A 24-page printable planner tailored to your zone. Planting dates, monthly task lists, harvest log, seed inventory, and succession charts — everything you need to plan a full season.