Castor Bean in Zone 5a & 5b
Ricinus communis
When to plant castor bean in zone 5b
Zones 5a and 5b share the same average frost dates in our data, so this page covers both.
Method: Direct sow: Direct-sow outside. Castor Bean doesn't transplant well, or doesn't need the extra time indoors.
| Start indoors | Not typically started indoors |
|---|---|
| Direct sow / transplant outside | May 17–May 24 |
| Estimated bloom | Aug 25–Sep 1 (~100 days after direct-sowing) |
Spacing: about 10 square feet per plant (square-foot-gardening spacing). Mature height: 6-10 ft.
Castor bean is included here so this site can state plainly what it is, rather than leaving a gardener to find out from a packet that does not say.
How castor bean fits zone 5's season
Zone 5b's frost-free window runs about 148 days, from May 10 to October 5. Castor Bean needs about 100 days from sowing to first harvest.
Good companions
No standout companions recorded yet for Castor Bean.
Where to buy castor bean seeds
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing castor bean" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 5b calendar · Full companion planting guide · Full plant profile · Plan your beds in the Garden Designer →
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Growing Castor Bean in USDA zone 5b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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