Delphinium in Zone 10a & 10b
Delphinium elatum
Yes, delphinium grows in zones 10a and 10b. Set out nursery plants in Sep–Nov. For a fall crop, plant out in Sep–Nov.
When to plant delphinium in zone 10b
Zones 10a and 10b share the same average frost dates, so this page covers both.
Method: Buy as a start: Buy as a nursery start and transplant outside. It's slow or unreliable from seed, so most gardeners skip seed-starting it entirely.
| Window | Fall window |
|---|---|
| Start indoors | Not started from seed; buy as a nursery start |
| Direct sow / transplant outside | Sep–Nov |
| Estimated bloom | ~150 days after transplanting |
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 3-6 ft.
Zone 10b dates sourced from growinginthegarden.com.
Fall window: the last sowing date is the average first frost minus days to maturity, the method in Purdue Extension's fall garden guide, which lists delphinium for late-summer planting.
Plant alongside it in zone 10b
These go outside within two weeks of delphinium in zone 10b, so one planting day can cover them.
- Bachelor's Button (Cornflower)Sep–Nov
- CalendulaSep–Nov
- Gaillardia (Blanket Flower)Sep–Nov
- LarkspurSep–Jan
- PetuniaSep–Mar
- SnapdragonSep–Feb
Delphinium produces some of the tallest, most dramatic flower spikes of any garden annual or perennial, in blues and purples that are hard to find elsewhere in a flower bed. It also comes with a serious caveat: every part of the plant is toxic if ingested.
How delphinium fits zone 10's season
Zone 10b's frost-free window runs about 324 days, from January 30 to December 20. Delphinium goes in during the fall and grows through the winter, so it isn't limited by this window: expect first bloom about 150 days after planting.
Delphinium planting windows in every zone
Zone 10b is highlighted. Useful for comparing against a neighbouring zone, or for a garden somewhere else.
| Zone | Start indoors | Sow or plant out | Bloom |
|---|---|---|---|
| 3a & 3b | Buy as a start | Jun 20–Jun 27 | Nov 17–Nov 24 |
| 4a & 4b | Buy as a start | Jun 5–Jun 12 | Nov 2–Nov 9 |
| 5a & 5b | Buy as a start | May 31–Jun 7 | Oct 28–Nov 4 |
| 6a & 6b | Buy as a start | May 16–May 23 | Oct 13–Oct 20 |
| 7a & 7b | Buy as a start | May 1–May 8 | Sep 28–Oct 5 |
| 8a & 8b | Buy as a start | Apr 15–Apr 22 | Sep 12–Sep 19 |
| 9a & 9b | Buy as a start | Mar 8–Mar 15 | Aug 5–Aug 12 |
| 10a & 10bFall window (your zone) | Buy as a start | Sep–Nov | ~150 days after transplanting |
Bloom dates are about 150 days after the sow or plant-out date.
Good companions
No well-established companions for delphinium.
Where to buy delphinium starts
Delphinium is almost always bought as a nursery start rather than seeded. Check a local nursery or garden center; we haven't vetted online start/plant suppliers yet.
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See it growing
Search YouTube for "growing delphinium" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 10b calendar · Plan your beds in the Garden Designer →
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Growing Delphinium in USDA zone 10b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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