Broccoli in Zone 6a & 6b
Brassica oleracea
Yes, broccoli grows in zones 6a and 6b. Start seeds indoors Mar 14–Mar 21 and plant out Apr 11–Apr 18. For a fall crop, start seeds indoors Jun 30–Jul 14 and plant out Jul 28–Aug 11.
When to plant broccoli 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.
| Window | Spring window |
|---|---|
| Start indoors | Mar 14–Mar 21 |
| Direct sow / transplant outside | Apr 11–Apr 18 |
| Estimated harvest | Jun 15–Jun 22 (~65 days after transplanting) |
| Window | Fall window |
|---|---|
| Start indoors | Jun 30–Jul 14 |
| Direct sow / transplant outside | Jul 28–Aug 11 |
| Estimated harvest | Oct 1–Oct 15 (~65 days after transplanting) |
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 1.5-2 ft.
Fall window: the last sowing date is the average first frost minus days to maturity, the method in Purdue Extension's fall garden guide, which lists broccoli for late-summer planting.
Plant alongside it in zone 6b
These go outside within two weeks of broccoli in zone 6b, so one planting day can cover them.
- RadishMar 28–Apr 4
- CarrotApr 4–Apr 11
- CabbageApr 11–Apr 18
- LettuceApr 11–Apr 18
- Flower SproutsApr 11–Apr 18
- Gai Lan (Chinese Broccoli)Apr 11–Apr 18
Broccoli is a cool-season crop wearing a warm-season crop's growing calendar in a lot of gardens. Start it too late in spring and heat pushes it to bolt into loose, bitter flower heads before it ever forms a proper crown.
How broccoli fits zone 6's season
Zone 6b's frost-free window runs about 173 days, from April 25 to October 15. Broccoli needs about 65 days from transplant to first harvest.
Broccoli 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 | Harvest |
|---|---|---|---|
| 2a & 2b | Apr 8–Apr 15 | May 6–May 13 | Jul 10–Jul 17 |
| 3a & 3b | Apr 18–Apr 25 | May 16–May 23 | Jul 20–Jul 27 |
| 4a & 4b | Apr 3–Apr 10 | May 1–May 8 | Jul 5–Jul 12 |
| 5a & 5bSpring window | Mar 29–Apr 5 | Apr 26–May 3 | Jun 30–Jul 7 |
| Fall window | Jun 20–Jul 4 | Jul 18–Aug 1 | Sep 21–Oct 5 |
| 6a & 6bSpring window (your zone) | Mar 14–Mar 21 | Apr 11–Apr 18 | Jun 15–Jun 22 |
| Fall window | Jun 30–Jul 14 | Jul 28–Aug 11 | Oct 1–Oct 15 |
| 7a & 7bSpring window | Feb 27–Mar 6 | Mar 27–Apr 3 | May 31–Jun 7 |
| Fall window | Jul 10–Jul 24 | Aug 7–Aug 21 | Oct 11–Oct 25 |
| 8a & 8bSpring window | Feb 11–Feb 18 | Mar 11–Mar 18 | May 15–May 22 |
| Fall window | Jul 26–Aug 9 | Aug 23–Sep 6 | Oct 27–Nov 10 |
| 9a & 9bSpring window | Jan 4–Jan 11 | Feb 1–Feb 8 | Apr 7–Apr 14 |
| Fall window | Aug 20–Sep 3 | Sep 17–Oct 1 | Nov 21–Dec 5 |
| 10a & 10bFall window | Aug–Dec | Sep–Jan | ~65 days after transplanting |
Harvest dates are about 65 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
- Onion: Onion scent is reputed to confuse cabbage moths that target brassicas. The research behind this is real but garlic-specific (field trials intercropping garlic with cabbage reduced diamondback moth damage): onion hasn't been tested the same way, so treat the onion version as a reasonable extrapolation, not a directly measured result.
Where to buy broccoli seeds
Botanical Interests · True Leaf Market · Burpee · High Mowing Organic Seeds (each supplier's broccoli seeds)
Varieties we recommend, and where to get them:
- 'Waltham 29' (best for fall crops, side shoots): Released in 1950 by the University of Massachusetts Waltham Field Station. Buy: Botanical Interests · True Leaf Market · Burpee · High Mowing Organic Seeds Full notes
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing broccoli" 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 Broccoli in USDA zone 6b: when to start seeds indoors, when to direct-sow, and when to expect a harvest.
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