Long beans
Vigna unguiculata subsp. sesquipedalis
Also known asYard-long beans · Snake beans · Asparagus beans · Sitao · Bodi
Environment
The bounded range this crop tolerates. Strict on light; outside the DLI band, yields drop sharply.
Climate and zones
- USDA zones
- 9–13 (winter low around -7°C)
- Frost
- frost sensitive (dies at first frost)
- Season
- year-round tropical
Growing systems
Root mass: moderate.
Growing media
| Medium | pH effect | Retention | Bacterial surface |
|---|---|---|---|
| Expanded clay pebbles (LECA) | neutral / inert | low | high |
| Coco coir (Coconut coir) | slightly acidic | high | moderate |
| Soil-based mix (Potting soil) | varies | high | high |
Nutrient demand by stage
NPK ratios are relative weights. EC targets shift through the plant's life.
| Stage | N | P | K | EC (mS/cm) |
|---|---|---|---|---|
| seedling | 1 | 1 | 1 | 1 |
| vegetative | 2 | 1 | 2 | 1.8 |
| flowering | 1 | 2 | 3 | 2.2 |
| fruiting | 1 | 2 | 4 | 2.4 |
Companion-growing notes
- Heavy uptake of potassium. Co-grown crops with the same demand will end up deficient even at "correct" EC.
- High transpiration. Regular reservoir top-ups needed during fruiting.
Aquaponics suitability
Compatible
Fish waste provides enough nitrogen for healthy growth. Supplemental potassium, calcium, and iron may still be needed depending on fish stocking density.
Care notes
A productive vine crop for warm hydroponic greenhouses. Dutch bucket or media bed with strong trellis (2 m). EC 1.5-2.5 mS/cm. pH 6.0-7.0. Temperature: 25–35°C (strictly tropical; growth stalls below 20°C). High light (DLI 18-25 mol/m2/day). From seed to first harvest: 55-70 days. The vines produce prolifically once flowering begins. Harvest pods when they're 30–45 cm long and still thin and flexible; overmaturity causes the pods to become tough and the seeds inside to swell. Daily harvesting during peak production keeps the vine fruiting. Each vine produces dozens of pods over a 2-3 month fruiting period. The pods should snap when bent; if they're rubbery and bend without snapping, they're overripe. As a legume, nitrogen fixation occurs via root nodules, reducing the need for supplemental N. The heat requirement limits long beans to tropical or heated-greenhouse conditions. For Asian vegetable markets, long beans are a high-volume, consistent seller.