Delphinium in Zone 7a & 7b
Delphinium elatum
Yes, delphinium grows in zones 7a and 7b. Set out nursery plants May 1–May 8.
When to plant delphinium in zone 7b
Zones 7a and 7b 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.
| Start indoors | Not started from seed; buy as a nursery start |
|---|---|
| Direct sow / transplant outside | May 1–May 8 |
| Estimated bloom | Sep 28–Oct 5 (~150 days after transplanting) |
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 3-6 ft.
Plant alongside it in zone 7b
These go outside within two weeks of delphinium in zone 7b, so one planting day can cover them.
- NasturtiumApr 17–Apr 24
- MarigoldApr 17–Apr 24
- Hyacinth Bean VineMay 1–May 8
- Angelonia (Summer Snapdragon)Apr 24–May 1
- Bee BalmApr 24–May 1
- Black-Eyed Susan VineApr 24–May 1
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 7's season
Zone 7b's frost-free window runs about 198 days, from April 10 to October 25. Delphinium needs about 150 days from transplant to first bloom.
Delphinium planting windows in every zone
Zone 7b 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 (your zone) | 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 | 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)
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Growing Delphinium in USDA zone 7b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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