Sea Kale in Zone 6a & 6b
Crambe maritima
Yes, sea kale grows in zones 6a and 6b and comes back each year. Plant it outside Apr 11–Apr 18.
When to plant sea kale in zone 6b
Zones 6a and 6b share the same average frost dates, so this page covers both.
Method: Direct sow: Direct-sow outside. It doesn't transplant well, or doesn't need the extra time indoors.
| Start indoors | Not typically started indoors |
|---|---|
| Direct sow / transplant outside | Apr 11–Apr 18 |
| Estimated harvest | First real harvest in year 3 |
Spacing: about 4 square feet per plant (square-foot-gardening spacing). Mature height: 1.5-2.5 ft.
Before you plant: Sea kale has a winter-hardiness note for zone 6b. See the details below.
Plant alongside it in zone 6b
These go outside within two weeks of sea kale in zone 6b, so one planting day can cover them.
- OnionApr 4–Apr 11
- CarrotApr 4–Apr 11
- CabbageApr 11–Apr 18
- LettuceApr 11–Apr 18
- BroccoliApr 11–Apr 18
- Flower SproutsApr 11–Apr 18
Sea kale is a Brassica-family perennial from European seashores that was a popular Victorian-era vegetable and has never quite managed a comeback since, despite being easy to grow in much of the US outside hot, humid summers.
How sea kale fits zone 6's season
Zone 6b's frost-free window runs about 173 days, from April 25 to October 15. Sea kale takes about 2 growing seasons to reach first worthwhile harvest, so what matters here is how many of these seasons it gets, not whether one is long enough.
Sea kale is hardy in zones 4-8, so in zone 6b it stays in the ground through winter and comes back rather than being replanted. Allow about 3 ft of spread at maturity.
Sea Kale 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 |
|---|---|---|---|
| 4a & 4b | Not usually | May 1–May 8 | First real harvest in year 3 |
| 5a & 5b | Not usually | Apr 26–May 3 | First real harvest in year 3 |
| 6a & 6b (your zone) | Not usually | Apr 11–Apr 18 | First real harvest in year 3 |
| 7a & 7b | Not usually | Mar 27–Apr 3 | First real harvest in year 3 |
| 8a & 8b | Not usually | Mar 11–Mar 18 | First real harvest in year 3 |
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. A different genus (Crambe) from most brassicas here, but the same family and the same flea-beetle vulnerability.
Where to buy sea kale seeds
None of the seed suppliers we list carries sea kale 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 sea kale" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
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Growing Sea Kale in USDA zone 6b: when to start seeds indoors, when to direct-sow, and when to expect a harvest.
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