Plant Sunflowers in Zone 9b
Seed-starting, transplant & harvest dates for USDA Zone 9b
Zone 9b averages 298 frost-free days, running from a last spring frost around February 15 to a first fall frost around December 10. Sunflowers needs roughly 80 days from planting out to first harvest, so it uses about 27 percent of that window. Sunflowers is a half-hardy crop, which is what decides where in the window it belongs.
Sunflowers resents transplanting and hates cold soil, so direct sow around Feb 22, after the Zone 9b last frost has passed and the soil has warmed. At 80 days to harvest, a 298-day Zone 9b season has room for about 3 sowings, so stagger them rather than planting everything at once.
Fall planting: sunflowers in Zone 9b
Sunflowers has no useful fall window in Zone 9b. Sunflowers need a long run of warm, long days and will not finish from a late-summer sowing outside frost-free zones.
Sunflowers need a long run of warm, long days and will not finish from a late-summer sowing outside frost-free zones.
Fall dates are counted backward from the Zone 9b average first frost, not forward from a sowing date. See the fall planting calendar by zone for the full method.
Spring vs fall sunflowers in Zone 9b
| Planting | Sow or start | In the ground | Harvest |
|---|---|---|---|
| Spring | Feb 22 | Feb 22 | May 13 |
| Fall | — | — | — |
Sunflowers in nearby zones
Further reading on sunflowers
- Last frost date and what to plant before it
Why sunflowers can go out before your last frost, and how far before.
- Companion planting chart
What to plant with sunflowers and what to keep away from it.
Other crops in Zone 9b
Frequently asked questions
When should I start sunflowers in Zone 9b?
Direct sow outdoors around Feb 22.
Can I direct sow sunflowers in Zone 9b?
Yes, direct sow around Feb 22.
Can I plant sunflowers in the fall in Zone 9b?
Sunflowers has no useful fall window in Zone 9b. Sunflowers need a long run of warm, long days and will not finish from a late-summer sowing outside frost-free zones.
Will sunflowers survive frost in Zone 9b?
No. Sunflowers is a half-hardy crop and a single light frost ends it, so every Zone 9b planting has to finish before the average first frost.
How many plantings of sunflowers fit in a Zone 9b season?
About 3. Zone 9b averages 298 frost-free days and sunflowers needs roughly 80 days plus a couple of weeks of turnaround, so sowing every 47 days keeps a supply coming.