Delphinium in Zone 6a & 6b
Delphinium elatum
Yes, delphinium grows in zones 6a and 6b. Set out nursery plants May 16–May 23.
When to plant delphinium in zone 6b
Zones 6a and 6b 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 16–May 23 |
| Estimated bloom | Oct 13–Oct 20 (~150 days after transplanting) |
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 3-6 ft.
Plant alongside it in zone 6b
These go outside within two weeks of delphinium in zone 6b, so one planting day can cover them.
- NasturtiumMay 2–May 9
- MarigoldMay 2–May 9
- Hyacinth Bean VineMay 16–May 23
- Angelonia (Summer Snapdragon)May 9–May 16
- Bee BalmMay 9–May 16
- Black-Eyed Susan VineMay 9–May 16
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 6's season
Zone 6b's frost-free window runs about 173 days, from April 25 to October 15. Delphinium needs about 150 days from transplant to first bloom.
Delphinium planting windows in every zone
Zone 6b 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 (your zone) | 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 | 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 6b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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