Sweet William in Zone 6a & 6b
Dianthus barbatus
Yes, sweet William grows in zones 6a and 6b. Start seeds indoors Mar 7–Mar 14 and plant out Apr 18–Apr 25.
When to plant sweet William in zone 6b
Zones 6a and 6b share the same average frost dates, so this page covers both.
Method: Start indoors: Start indoors from seed, then transplant outside. It needs a head start most zones can't give it by direct-sowing alone.
| Start indoors | Mar 7–Mar 14 |
|---|---|
| Direct sow / transplant outside | Apr 18–Apr 25 |
| Estimated bloom | Jun 17–Jun 24 (~60 days after transplanting) |
Spacing: 4 per square foot (square-foot-gardening spacing). Mature height: 1-2 ft.
Plant alongside it in zone 6b
These go outside within two weeks of sweet William in zone 6b, so one planting day can cover them.
- NasturtiumMay 2–May 9
- MarigoldMay 2–May 9
- Bells of IrelandApr 18–Apr 25
- CarnationApr 18–Apr 25
- Orlaya (Laceflower)Apr 18–Apr 25
- Phlox (Annual)Apr 18–Apr 25
Sweet William is a cottage-garden staple, grown for dense clusters of small, fragrant flowers that often come bicolor, a ring of contrasting color around each petal's edge. NC State Extension puts it at 1 to 2 feet tall and 6 inches to a foot wide, in pink, purple, red, white and variegated forms, hardy across zones 3a to 9b.
How sweet William fits zone 6's season
Zone 6b's frost-free window runs about 173 days, from April 25 to October 15. Sweet William needs about 60 days from transplant to first bloom.
Sweet William 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 | Apr 11–Apr 18 | May 23–May 30 | Jul 22–Jul 29 |
| 4a & 4b | Mar 27–Apr 3 | May 8–May 15 | Jul 7–Jul 14 |
| 5a & 5b | Mar 22–Mar 29 | May 3–May 10 | Jul 2–Jul 9 |
| 6a & 6b (your zone) | Mar 7–Mar 14 | Apr 18–Apr 25 | Jun 17–Jun 24 |
| 7a & 7b | Feb 20–Feb 27 | Apr 3–Apr 10 | Jun 2–Jun 9 |
| 8a & 8b | Feb 4–Feb 11 | Mar 18–Mar 25 | May 17–May 24 |
| 9a & 9b | Dec 28–Jan 4 | Feb 8–Feb 15 | Apr 9–Apr 16 |
Bloom dates are about 60 days after the sow or plant-out date, not after starting seeds indoors.
Good companions
No well-established companions for sweet William.
Where to buy sweet William seeds
Botanical Interests · True Leaf Market · High Mowing Organic Seeds (each supplier's sweet William seeds)
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See it growing
Search YouTube for "growing sweet William" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 6b calendar · Plan your beds in the Garden Designer →
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Growing Sweet William in USDA zone 6b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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