Long beans
Vigna unguiculata subsp. sesquipedalis
Also known as: Yard-long beans, Snake beans, Asparagus beans, Sitao, Bodi
Quick facts
- Category
- fruiting
- Difficulty
- beginner
- Days to harvest
- 60 to 90 days
- Harvest type
- continuous production over weeks or months
- Spacing
- 30 cm between plants
Environment
- Temperature
- 20–35°C
- pH
- 6 to 7
- EC (hydroponic)
- 1.8 to 2.5 mS/cm
- Daily light
- 20 to 28 mol/m²/day (strict, will fail outside this range)
Climate and zones
- USDA zones
- 9 to 13 (winter low around -7°C or warmer)
- Frost tolerance
- frost sensitive (dies at first frost)
- Season
- year-round tropical (needs consistent warmth)
Viable growing environments:
- outdoor in growing season (annual)
- heated greenhouse
- indoor (heated home)
- indoor hydroponics under grow lights
USDA zone bounds reflect outdoor year-round survival. Anywhere outside the bounded zone range, this crop still grows as an annual in the warm months (outdoor_seasonal), under cover (greenhouse), or indoors under lights.
Growing systems
Long beans works in:
- media bed (ebb and flow)
- wicking bed
- soil bed
- drip / Dutch buckets
Growing media
The substrate the roots sit in. Choice depends on the system (clay pebbles don't fit NFT channels; rockwool isn't used in media beds) and the crop (long beans works in the media listed below).
| Medium | pH effect | Water 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 by source | high | high |
Bacterial surface area matters for aquaponics: clay pebbles, lava rock, and pumice double as biofilter substrate. Low-surface media (rockwool, perlite, pea gravel) work in hydroponics but need a separate biofilter in aquaponics.
Nutrient demand by stage
NPK ratios are relative weights at each growth stage; the nutrient mix calculator scales them to absolute grams or ml. EC targets shift through the plant's life: seedlings need a much lighter solution than fruiting adults.
| Stage | N | P | K | EC target (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. Plan around this in shared reservoirs.
- High transpiration. Reservoir level will need regular top-ups during fruiting or flowering.
Aquaponics suitability
Compatible with typical aquaponics nutrient profiles. 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.
Verified against: rhs-uk, university-of-florida-ifas. Last reviewed 2026-05-15.