Bachelor's Button (Cornflower) in Zone 4a & 4b
Centaurea cyanus
Yes, bachelor's button (cornflower) grows in zones 4a and 4b. Start seeds indoors Mar 27–Apr 3 and plant out May 1–May 8.
When to plant bachelor's button (cornflower) in zone 4b
Zones 4a and 4b share the same average frost dates, so this page covers both.
Method: Either: Start indoors for an earlier harvest, or direct-sow outside for less fuss. Either works.
| Start indoors | Mar 27–Apr 3 |
|---|---|
| Direct sow / transplant outside | May 1–May 8 |
| Estimated bloom | Jul 15–Jul 22 (~75 days after planting) |
Spacing: 3 per square foot (square-foot-gardening spacing). Mature height: 1-3 ft.
Plant alongside it in zone 4b
These go outside within two weeks of bachelor's button (cornflower) in zone 4b, so one planting day can cover them.
- Agrostemma (Corn Cockle)May 1–May 8
- AstilbeMay 1–May 8
- Basket-of-GoldMay 1–May 8
- Bupleurum (Thoroughwax)May 1–May 8
- CalendulaMay 1–May 8
- California PoppyMay 1–May 8
Bachelor's button (also sold as cornflower) is about as low-effort as annual flowers get. It tolerates cold better than most, fills in fast, and doesn't ask for much once it's in the ground. Wiry 1- to 3-foot stems carry small, fringed, frilly round blooms, most often blue, though pink, white, and maroon show up in mixes too.
How bachelor's button (cornflower) fits zone 4's season
Zone 4b's frost-free window runs about 128 days, from May 15 to September 20. Bachelor's button (cornflower) needs about 75 days from sowing to first bloom.
Bachelor's Button (Cornflower) planting windows in every zone
Zone 4b is highlighted. Useful for comparing against a neighbouring zone, or for a garden somewhere else.
| Zone | Start indoors | Sow or plant out | Bloom |
|---|---|---|---|
| 2a & 2b | Apr 1–Apr 8 | May 6–May 13 | Jul 20–Jul 27 |
| 3a & 3b | Apr 11–Apr 18 | May 16–May 23 | Jul 30–Aug 6 |
| 4a & 4b (your zone) | Mar 27–Apr 3 | May 1–May 8 | Jul 15–Jul 22 |
| 5a & 5b | Mar 22–Mar 29 | Apr 26–May 3 | Jul 10–Jul 17 |
| 6a & 6b | Mar 7–Mar 14 | Apr 11–Apr 18 | Jun 25–Jul 2 |
| 7a & 7b | Feb 20–Feb 27 | Mar 27–Apr 3 | Jun 10–Jun 17 |
| 8a & 8b | Feb 4–Feb 11 | Mar 11–Mar 18 | May 25–Jun 1 |
| 9a & 9b | Dec 28–Jan 4 | Feb 1–Feb 8 | Apr 17–Apr 24 |
| 10a & 10bFall window | Not usually | Sep–Nov | ~75 days after planting |
| 11a & 11b | Nov 13–Nov 20 | Dec 18–Dec 25 | Mar 3–Mar 10 |
Bloom dates are about 75 days after the sow or plant-out date, not after starting seeds indoors.
Zone 2 sows before zone 3 here, which looks wrong and is not. USDA zones rank winter cold, not season length, and zone 2 is mostly interior Alaska, where hard winters come with warm summers. More on what a zone measures.
Good companions
No well-established companions for bachelor's button (cornflower).
Where to buy bachelor's button seeds
Botanical Interests · True Leaf Market · High Mowing Organic Seeds (each supplier's bachelor's button seeds)
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing bachelor's button (cornflower)" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 4b calendar · Plan your beds in the Garden Designer →
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Growing Bachelor's Button (Cornflower) in USDA zone 4b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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