Sweet William in Zone 3a & 3b
Dianthus barbatus
Yes, sweet William grows in zones 3a and 3b. Start seeds indoors Apr 11–Apr 18 and plant out May 23–May 30.
When to plant sweet William in zone 3b
Zones 3a and 3b 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 | Apr 11–Apr 18 |
|---|---|
| Direct sow / transplant outside | May 23–May 30 |
| Estimated bloom | Jul 22–Jul 29 (~60 days after transplanting) |
Spacing: 4 per square foot (square-foot-gardening spacing). Mature height: 1-2 ft.
Plant alongside it in zone 3b
These go outside within two weeks of sweet William in zone 3b, so one planting day can cover them.
- NasturtiumJun 6–Jun 13
- MarigoldJun 6–Jun 13
- Bells of IrelandMay 23–May 30
- CarnationMay 23–May 30
- Orlaya (Laceflower)May 23–May 30
- Phlox (Annual)May 23–May 30
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 3's season
Zone 3b's frost-free window runs about 98 days, from May 30 to September 5. Sweet William needs about 60 days from transplant to first bloom.
Sweet William planting windows in every zone
Zone 3b 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 (your zone) | 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 | 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 3b calendar · Plan your beds in the Garden Designer →
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Growing Sweet William in USDA zone 3b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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