Growing Thai basil

Thai basil (*Ocimum basilicum* var. *thyrsiflora*) is a variety of sweet basil with a distinctly different flavor profile -- more anise and clove character, less sweet and peppery than Genovese or Italian basil. It is the type used in Thai, Vietnamese, and other Southeast Asian cuisines. Per NC.

Thai basil (Ocimum basilicum var. thyrsiflora) is a variety of sweet basil with a distinctly different flavor profile — more anise and clove character, less sweet and peppery than Genovese or Italian basil. It is the type used in Thai, Vietnamese, and other Southeast Asian cuisines. Per NC State Extension, it is also more heat-tolerant than most sweet basil varieties and more resistant to wilting in full summer sun.

The visual differences are easy to identify: Thai basil has purple stems, purple-tinged leaves, and purple flower buds, compared to the green stems of Italian basil. The flavor difference is significant enough that they are not interchangeable in most recipes.

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Zones and timing

Thai basil is a frost-tender annual in all zones below 10. Per Clemson HGIC, do not transplant or direct-sow until nighttime temperatures consistently stay above 50°F and soil temperature is at least 60°F. Cold soil causes purple discoloration of leaves, slow growth, and poor establishment.

Per Cornell Cooperative Extension, Thai basil can be started indoors 4–6 weeks before the last frost date under grow lights (16 hours of light per day) and transplanted after hardening off over 7–10 days.