Thai basil
Ocimum basilicum var. thyrsiflora
Also known asHorapha · Bai horapa · Anise basil · Licorice basil
Environment
The bounded range this crop tolerates.
Climate and zones
- USDA zones
- 10–13 (winter low around -1°C)
- Frost
- frost sensitive (dies at first frost)
- Season
- warm (summer, frost-sensitive)
Growing systems
Root mass: moderate.
Growing media
| Medium | pH effect | Retention | Bacterial surface |
|---|---|---|---|
| Rockwool (Mineral wool) | alkaline until pre-soaked | very high | low |
| Expanded clay pebbles (LECA) | neutral / inert | low | high |
| Coco coir (Coconut coir) | slightly acidic | high | moderate |
| Net pot, no medium (Bare-root) | - | - | - |
| 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 | 0.8 |
| vegetative | 3 | 1 | 2 | 1.4 |
Companion-growing notes
- 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
Care is much like Genovese basil but with a little more heat tolerance. Hold EC around 1.0-1.6 mS/cm and pH 5.5-6.5. Keep temperatures 22–32°C; it takes heat better than Italian basil but still suffers below 15°C. Give high light, on the order of 18-25 mol/m2/day. It grows in all the standard hydroponic systems, with a first cut about five to six weeks from seed, a touch slower to establish than Genovese. Pinch the growing tips to force branching, the same as Italian basil. It bolts less aggressively than Genovese, and the purple flowers are edible and make a good garnish. The flavour cannot be swapped for Italian basil in Southeast Asian dishes. For anyone who regularly cooks Thai or Vietnamese food, a couple of plants give a steady supply of an herb that is often pricey or hard to find fresh in supermarkets.
Notable varieties
| Cultivar | Type | Days | Notes |
|---|---|---|---|
| Siam Queen | hybrid | 65 | 1997 All-America Selections winner. The most-grown Thai basil in Western markets. Strong anise-licorice flavor, dark green leaves with purple stems. Slow to bolt for a Thai-type basil. |
| Thai Holy Basil (Kaprao) | open pollinated | 70 | Ocimum tenuiflorum (tulsi), a different species from Thai sweet basil. Spicy, peppery, clove-like; the basil in true pad kaprao. Not interchangeable with Genovese or Siam Queen. |
| Lemon Basil | open pollinated | 65 | Ocimum x africanum (formerly O. x citriodorum). Strong lemon scent over a basil base. Used in Thai and Indonesian fish dishes. Bolts faster than other basils; succession-plant every 4-6 weeks. |