When to plant / Sunflowers
When to plant sunflowers
Plant sunflowers after the last spring frost, once the soil is warm, and no later than 45 days before the first fall frost so the quickest variety can finish. Across the 39 U.S. cities on this site the window opens between Feb 9 (Sacramento, CA) and May 13 (Concord, NH) and the last sensible sowing falls between Aug 16 and Oct 24.
The planting rule for sunflowers, in plain words
Sunflowers are frost-tender and need warm soil. Oregon State University Extension: plant wait until after the last frost when soil temperatures have reached at least 50°F.
, when once the danger of frost has passed and soils have warmed to above 50°F
The end of the window is arithmetic. Oregon State's cultivar table runs from 45 to 95 days to maturity. Counting the shortest figure, 45 days, back from a station's first fall frost gives the last date a quick variety can be sown and still finish; counting 95 days back gives the deadline for the slowest. Both appear in the table. Oregon State: Sunflowers can be grown either by direct sowing or as transplants.
Sow Plant seeds about 1 inch deep
; Larger, branching varieties should be spaced 18 to 24 inches apart
, while single stem varieties can be spaced as close as 4 to 6 inches apart
Soil temperature for sunflowers
Minimum soil temperature for sunflowers in the cited sources: 50°F (both sources: wait for soil of at least 50°F after the last frost). A frost date cannot see the soil, so take a morning reading before trusting the window; the soil temperature guide covers every crop.
Sunflowers: planting dates for 39 U.S. cities
The rule above applied to each station's own NOAA normals, earliest first. City links open that station's full calendar.
| City | Last spring frost (32°F) | Direct sow (or transplant) | Last sowing (45-day variety) | Last sowing (95-day variety) |
|---|---|---|---|---|
| Sacramento, CA | Feb 9 | Feb 9 – Oct 19 | Oct 19 | Aug 30 |
| Houston, TX | Feb 18 | Feb 18 – Oct 24 | Oct 24 | Sep 4 |
| Austin, TX | Feb 19 | Feb 19 – Oct 22 | Oct 22 | Sep 2 |
| San Antonio, TX | Mar 1 | Mar 1 – Oct 17 | Oct 17 | Aug 28 |
| Dallas–Fort Worth, TX | Mar 8 | Mar 8 – Oct 11 | Oct 11 | Aug 22 |
| Seattle, WA | Mar 8 | Mar 8 – Oct 7 | Oct 7 | Aug 18 |
| Portland, OR | Mar 16 | Mar 16 – Oct 3 | Oct 3 | Aug 14 |
| Atlanta, GA | Mar 20 | Mar 20 – Oct 7 | Oct 7 | Aug 18 |
| Birmingham, AL | Mar 27 | Mar 27 – Sep 28 | Sep 28 | Aug 9 |
| Oklahoma City, OK | Mar 27 | Mar 27 – Sep 25 | Sep 25 | Aug 6 |
| Washington, DC | Mar 28 | Mar 28 – Oct 3 | Oct 3 | Aug 14 |
| New York City | Apr 1 | Apr 1 – Oct 4 | Oct 4 | Aug 15 |
| Philadelphia, PA | Apr 2 | Apr 2 – Sep 26 | Sep 26 | Aug 7 |
| Louisville, KY | Apr 3 | Apr 3 – Sep 20 | Sep 20 | Aug 1 |
| Raleigh, NC | Apr 3 | Apr 3 – Sep 20 | Sep 20 | Aug 1 |
| St. Louis, MO | Apr 3 | Apr 3 – Sep 19 | Sep 19 | Jul 31 |
| Charlotte, NC | Apr 4 | Apr 4 – Sep 19 | Sep 19 | Jul 31 |
| Richmond, VA | Apr 4 | Apr 4 – Sep 20 | Sep 20 | Aug 1 |
| Boston, MA | Apr 6 | Apr 6 – Sep 24 | Sep 24 | Aug 5 |
| Nashville, TN | Apr 6 | Apr 6 – Sep 18 | Sep 18 | Jul 30 |
| Kansas City, MO | Apr 12 | Apr 12 – Sep 8 | Sep 8 | Jul 20 |
| Columbus, OH | Apr 16 | Apr 16 – Sep 12 | Sep 12 | Jul 24 |
| Indianapolis, IN | Apr 16 | Apr 16 – Sep 7 | Sep 7 | Jul 19 |
| Des Moines, IA | Apr 17 | Apr 17 – Sep 2 | Sep 2 | Jul 14 |
| Detroit, MI | Apr 20 | Apr 20 – Sep 9 | Sep 9 | Jul 21 |
| Omaha, NE | Apr 21 | Apr 21 – Aug 27 | Aug 27 | Jul 8 |
| Salt Lake City, UT | Apr 21 | Apr 21 – Sep 9 | Sep 9 | Jul 21 |
| Chicago, IL | Apr 22 | Apr 22 – Sep 4 | Sep 4 | Jul 16 |
| Cleveland, OH | Apr 22 | Apr 22 – Sep 16 | Sep 16 | Jul 28 |
| Hartford, CT | Apr 24 | Apr 24 – Aug 29 | Aug 29 | Jul 10 |
| Pittsburgh, PA | Apr 24 | Apr 24 – Sep 5 | Sep 5 | Jul 17 |
| Minneapolis, MN | Apr 25 | Apr 25 – Aug 26 | Aug 26 | Jul 7 |
| Albany, NY | Apr 28 | Apr 28 – Aug 26 | Aug 26 | Jul 7 |
| Grand Rapids, MI | Apr 28 | Apr 28 – Sep 1 | Sep 1 | Jul 13 |
| Portland, ME | May 1 | May 1 – Aug 26 | Aug 26 | Jul 7 |
| Madison, WI | May 2 | May 2 – Aug 21 | Aug 21 | Jul 2 |
| Burlington, VT | May 4 | May 4 – Aug 24 | Aug 24 | Jul 5 |
| Denver, CO | May 6 | May 6 – Aug 22 | Aug 22 | Jul 3 |
| Concord, NH | May 13 | May 13 – Aug 16 | Aug 16 | Jun 27 |
"Season too short" means the 95-day deadline falls before the last frost date, so only a quicker variety fits between the two frosts without protection. In the longest seasons the arithmetic runs into late summer; it counts frost only and says nothing about heat.
3 frost-free stations are left out. Not in the table? The planner takes any pair of frost dates.
Three cities, one rule
- Sacramento, California — last spring frost Feb 9, so direct sow (or transplant) Feb 9 – Oct 19; last sowing for a 45-day variety Oct 19. 297 frost-free days in all.
- Kansas City, Missouri — last spring frost Apr 12, so direct sow (or transplant) Apr 12 – Sep 8; last sowing for a 45-day variety Sep 8. 194 frost-free days in all.
- Concord, New Hampshire — last spring frost May 13, so direct sow (or transplant) May 13 – Aug 16; last sowing for a 45-day variety Aug 16. 140 frost-free days in all.
Questions about planting sunflowers
When can I plant sunflowers outside?
After the last spring frost, once the soil is at least 50°F. The frost date is Feb 9 in Sacramento, CA and May 13 in Concord, NH; the soil reading can lag it by weeks in a cold spring.
When is it too late to plant sunflowers?
Count the variety's days to maturity back from the first fall frost. For a 45-day variety the last sowing is Oct 19 in Sacramento, CA and Aug 16 in Concord, NH; a 95-day variety needs to be in 50 days sooner.
Should I start sunflowers indoors?
Oregon State says sunflowers can be direct-sown or transplanted, with transplants going out after the frost date in the table. Direct sowing is the simpler route; 45-day cultivars fit every city in the table.
How many sunflowers cities have room for a 95-day variety?
39 of the 39 cities in the table can sow a 95-day variety on or after the last frost date and still finish before the first fall frost. The others need a quicker variety or season extension.
When do I harvest sunflowers?
Oregon State's cultivar table runs 45 to 95 days from sowing to maturity, so a sowing on the frost date in Kansas City, MO (Apr 12) matures roughly 45 to 95 days later.
Related planting dates
- When to plant pumpkins — after the last spring frost, once the soil has warmed
- When to plant zucchini — from the last spring frost date to 1 week after it
- When to plant tulips — in fall, before the first frost
- All crops · calendars by city · cool-season vs warm-season crops
Sources for this page
| Source | Used for | Read |
|---|---|---|
| NOAA/NCEI U.S. Climate Normals 1991–2020 | 50% probability last spring and first fall 32°F and 28°F dates for each station | 2026-10-16 |
| Oregon State University Extension, EM 9866 Grow Your Own Sunflowers | quoted timing, soil temperature, maturity or depth statements | 2026-10-23 |
| Clemson Cooperative Extension HGIC, Let's Grow Sunflowers | quoted timing, soil temperature, maturity or depth statements | 2026-10-23 |
Every date in the table is arithmetic on the station's NOAA normal and the offset stated by the source; the quoted sentences are the only figures on this page that are not computed. Normals are 30-year averages and describe the station, not your yard. Rules checked 2026-10-23; see the methodology page.