Climate matters. This page is a practical baseline. Confirm cultivar, local frost/heat conditions, mature size and regional restrictions before planting.
Sunn Hemp — Growing reference
| Scientific name | Crotalaria juncea |
|---|---|
| Seed germination (days) | 5–10 |
| Soil temperature for germination (°C) | 18.3–35 |
| First harvest or flowering (days) | 60–90 |
| Measured from | Seed |
| Plant spacing (cm) | 2.5–7.6 |
| Mature height (cm) | 121.9–304.8 |
| Mature spread (cm) | 10.2–20.3 |
| USDA hardiness zones | 9–11 |
| Light | Full sun |
| Water | Moderate |
| Sowing method | Direct sow |
Growing directions
Broadcast or drill seed 1/2 in deep into warm, well-drained soil after danger of frost has passed. Sunn hemp grows rapidly — up to 6 feet in two months — and fixes 100–200 lb of nitrogen per acre while suppressing root-knot nematodes through root exudates. Terminate by mowing at first bloom (roughly 60–70 days) before seed set, since mature plants become woody and slow to decompose. Do not plant where livestock can graze, as the foliage contains alkaloids toxic to most grazing animals.
Source and local conditions
Typical planning ranges from OpenPlantDB (CC0). Cultivar, climate, season and growing method can change these values. Confirm the seed label and local guidance before planting.
Source & verification
OpenPlantDB · CC0