Tropical Asian legume — perennial in true tropics, grown as an annual elsewhere. Reaches 2 m in 60 days, producing extraordinary biomass for nitrogen fixation and mulch.
Hardiness ratings
| System | Rating | Temperature range | How to read it |
|---|---|---|---|
| USDA hardiness zone | Zone 3–12 | −40 °C to 15.6 °C | Zones where it can be grown as an annual — not a frost-tolerance rating |
| RHS hardiness rating | H7 | down to −20 °C | Plant needs at least this level of cold tolerance |
| Canadian plant hardiness zone | Zone 3–9 | −34 °C and warmer | Zones where it can be grown as an annual — not a frost-tolerance rating |
| Australian (ANBG) zone | Zone 1–7 | −15 °C and warmer | Zones where it can be grown as an annual — not a frost-tolerance rating |
As a tender annual, Sunn hemp doesn't overwinter — the zone range shows where the growing season supports it. See the RHS rating for its actual cold tolerance.
Growing notes
- Other Crotalaria species are toxic to livestock — only C. juncea is safe
- Frost-tender — sow only in warm soil after last frost
- Excellent biomass producer — terminate at 50–60 days for maximum nitrogen contribution
Categories
Related plants
Cross-check Sunn hemp against your zones