Thai basil
Ocimum basilicum var. thyrsiflora
Also known asHoly basil (sometimes confused) · Holy basil (related Tulsi) · Horapha · Bai horapa
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
Similar hydroponic requirements to Genovese basil but slightly more heat-tolerant. EC 1.0-1.8 mS/cm. pH 5.5-6.5. Temperature: 22–32°C (handles heat better than Italian basil; still sensitive to cold below 15°C). High light (DLI 15-25 mol/m2/day). Grows in all standard hydroponic systems. From seed to first harvest: 5-6 weeks (slightly slower to establish than Genovese). Pinch growing tips to promote branching, same as Italian basil. Thai basil bolts (flowers) less aggressively than Genovese, and the purple flowers are edible and attractive as garnish. The flavor is distinctive and cannot be substituted with Italian basil in Southeast Asian dishes. The anise-licorice component comes from higher concentrations of methyl chavicol (estragole) in the essential oil. Grows slightly taller and rangier than Genovese (50–70 cm). For home cooks who regularly prepare Thai, Vietnamese, or other Southeast Asian food, a few Thai basil plants in a hydroponic system provide a steady supply of an herb that's often expensive or unavailable at regular 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, technically a different species from Thai Sweet Basil. Spicy, peppery, slightly clove-like; the basil in pad kaprao stir-fry. Less sweet than Genovese or Siam Queen; not interchangeable with them. |
| Lemon Basil | open pollinated | 65 | Ocimum × citriodorum (hybrid species). Strong lemon scent on top of basil flavor. Used in Thai and Indonesian fish dishes. Faster bolting than other basils; succession-plant every 4-6 weeks. |