Thai basil

Quick facts

Category

herbs soft

Difficulty

beginner

Days to harvest

45 to 65 days

Harvest type

cut leaves, plant regrows for repeated harvests

Spacing

25 cm between plants

Environment

Temperature

18–30°C

pH

5.5 to 6.5

EC (hydroponic)

1 to 1.6 mS/cm

Daily light

18 to 25 mol/m²/day

Climate and zones

USDA zones

10 to 13 (winter low around -1°C or warmer)

Frost tolerance

frost sensitive (dies at first frost)

Season

warm (summer crops, frost-sensitive)

Viable growing environments:

• outdoor year-round (in zone)
• outdoor in growing season (annual)
• unheated greenhouse / hoop house
• 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

Thai basil works in:

• deep water culture (rafts)
• NFT channels
• vertical / aeroponic tower
• media bed (ebb and flow)
• wicking bed
• drip / Dutch buckets
• soil bed

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 (thai basil works in the media listed below).

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.

Companion-growing notes

• 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

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

A starting shortlist of cultivars worth knowing about. Not exhaustive: the seed catalogs list hundreds of named varieties. These are the ones home growers commonly choose between.

Further reading

• Best crops for hydroponic beginners
• The Kratky method: grow lettuce with zero electricity