Broccolini in Zone 4a & 4b
Brassica oleracea var. italica x alboglabra
Yes, broccolini grows in zones 4a and 4b. Start seeds indoors Apr 10–Apr 17 and plant out May 15–May 22.
When to plant broccolini in zone 4b
Zones 4a and 4b 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 10–Apr 17 |
|---|---|
| Direct sow / transplant outside | May 15–May 22 |
| Estimated harvest | Jul 9–Jul 16 (~55 days after transplanting) |
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 1.5-2 ft.
Plant alongside it in zone 4b
These go outside within two weeks of broccolini in zone 4b, so one planting day can cover them.
- CabbageMay 1–May 8
- TomatoMay 29–Jun 5
- Bush BeansMay 22–May 29
- Sweet CornMay 22–May 29
- LettuceMay 1–May 8
- CucumberMay 22–May 29
Broccolini is a cross between broccoli and gai lan, both of which this site already covers separately. It is worth its own square because you harvest it on a completely different rhythm.
How broccolini fits zone 4's season
Zone 4b's frost-free window runs about 128 days, from May 15 to September 20. Broccolini needs about 55 days from transplant to first harvest.
Broccolini 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 | Harvest |
|---|---|---|---|
| 2a & 2b | Apr 15–Apr 22 | May 20–May 27 | Jul 14–Jul 21 |
| 3a & 3b | Apr 25–May 2 | May 30–Jun 6 | Jul 24–Jul 31 |
| 4a & 4b (your zone) | Apr 10–Apr 17 | May 15–May 22 | Jul 9–Jul 16 |
| 5a & 5b | Apr 5–Apr 12 | May 10–May 17 | Jul 4–Jul 11 |
| 6a & 6b | Mar 21–Mar 28 | Apr 25–May 2 | Jun 19–Jun 26 |
| 7a & 7b | Mar 6–Mar 13 | Apr 10–Apr 17 | Jun 4–Jun 11 |
| 8a & 8b | Feb 18–Feb 25 | Mar 25–Apr 1 | May 19–May 26 |
| 9a & 9b | Jan 11–Jan 18 | Feb 15–Feb 22 | Apr 11–Apr 18 |
| 10a & 10b | Dec 26–Jan 2 | Jan 30–Feb 6 | Mar 26–Apr 2 |
Harvest dates are about 55 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
- Radish: Radish (including the daikon form) is a documented trap crop for flea beetles, which prefer its mustard oils over other brassicas and can be sacrificed or pulled once infested: the same research cited on the radish page.
Where to buy broccolini seeds
None of the seed suppliers we list carries broccolini seeds right now. A local garden center or a specialty seed house is the place to look.
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing broccolini" 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 Broccolini in USDA zone 4b: when to start seeds indoors, when to direct-sow, and when to expect a harvest.
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