Yam
Dioscorea alata
Also known asTrue yam · Water yam · Greater yam · Winged yam · Ñame · Ube · Igname
Environment
The bounded range this crop tolerates.
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: very heavy. Thin-channel systems can't hold this crop.
Growing media
| Medium | pH effect | Retention | Bacterial surface |
|---|---|---|---|
| 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 | 0.7 |
| vegetative | 2 | 1 | 3 | 1.5 |
Companion-growing notes
- Heavy uptake of potassium. Co-grown crops with the same demand will end up deficient even at "correct" EC.
Aquaponics suitability
Not recommended
Fish waste alone doesn't supply enough of what this crop demands. Grows in hybrid systems with supplemental dosing, but expect active management.
Care notes
A tropical vine crop requiring warm conditions and a long growing season. Large containers (30 L) or in-ground with strong trellis (the vines grow 2–5 m). EC 1.5-2.5 mS/cm. pH 5.5-7.0. Temperature: 25–35°C (strictly tropical; the tubers rot in cold soil below 15°C). High light (DLI 18-28 mol/m2/day). Propagation: from small tuber pieces or the top portion of a harvested tuber (the 'head' with growth buds). Plant 10–15 cm deep. The vine grows through the warm season; tubers develop underground over 6-12 months. Harvest when the vine dies back naturally. The long growing season makes true yams impractical in temperate climates without heated greenhouses. For tropical aquaponics operators, yams in media beds irrigated by the fish system produce well. The D. alata (ube) variety produces the vibrant purple color used in Filipino ice cream, cake, and jam.
Notable varieties
| Cultivar | Type | Days | Notes |
|---|---|---|---|
| Ube (purple yam) | open pollinated | 300 | Filipino purple-fleshed cultivar of D. alata, used in ube halaya, ice cream, and pastries. Vivid violet flesh; the color is anthocyanin-based and survives cooking. The variety driving the recent US specialty-market interest in true yams. |
| White Lisbon | open pollinated | 270 | Caribbean white-fleshed D. alata cultivar widely grown across Jamaica, Cuba, and the Dominican Republic. The yam most common in Caribbean market stalls. Stores 4-6 months at room temperature without sprouting. |
| Chinese yam (D. polystachya) | open pollinated | 210 | Different species; mentioned here because it's the cold-tolerant yam that growers in zones 6-8 can produce. Slimmer roots than D. alata, traditional Chinese medicine and cooking use (山药 shānyào). Invasive in parts of the US Southeast; check before planting. |