How to Grow Thai Basil From Seed

Thai basil is a heat-loving, warm-season herb, so let warmth guide your timing rather than the calendar. Start seeds indoors about 6 weeks before your last spring frost, then move plants outside only once nights stay reliably above 50F and the soil has warmed. You can also direct-sow once frost is well past and the ground is warm. Because it loves heat, Thai basil often outlasts sweet basil deep into summer, and you can keep sowing fresh batches for a steady supply.

Thai basil is easy to start from seed. Sow the small seeds about a quarter inch deep in rich, well-drained soil or moist seed-starting mix, and press them in gently for good soil contact. Keep the mix evenly moist and warm, around 70F, and seedlings usually appear in 5 to 10 days. Give them plenty of bright light so they stay stout, and once plants have a few sets of true leaves, thin or space them 8 to 12 inches apart in full sun.

Thai basil thrives in heat and rewards regular picking with sturdy, aromatic growth. Water to keep the soil evenly moist but never soggy, watering at the base in the morning so leaves dry quickly. Give it full sun and a light feed, and pinch the tips once plants reach 6 inches to build a bushy plant. It naturally sends up handsome purple flower spikes; leave a few for looks and pollinators, but pinch most off to keep the leaves coming. Because it loves warmth even more than sweet basil, growers across the South and Southwest, from Florida to Arizona, get a long, easy season, while gardeners in cooler regions like New England or the Pacific Northwest should wait for settled warm weather and nights above 50 degrees before transplanting, and often do best growing it in a warm, sheltered spot or a container against a sunny wall.

Thai basil is a fine garden neighbor, especially for tomatoes, and its strong anise scent helps deter many common pests. These four make especially good companions, and you can add any of them in one click:

Start picking once plants are 6 to 8 inches tall and bushy. Harvest by pinching or snipping whole stem tips just above a pair of leaves rather than stripping single leaves, which prompts the plant to branch and produce more. Cut in the morning when the aromatic oils are strongest, harvest often to keep it productive, and never take more than about a third of the plant at once.

Cook with Thai basil the way Thai and Vietnamese kitchens do: toss whole leaves into stir-fries like pad krapow in the last minute, pile them fresh onto bowls of pho and noodle soups at the table, and fold them into curries and spring rolls. Its bold anise-and-clove flavor holds up to a little heat better than sweet basil, but it still fades if overcooked, so add it late or use it raw. The sturdy leaves and purple stems also make a striking garnish.

• Bolting (flowering): Thai basil flowers readily in heat. Pinch off most flower spikes and harvest often to keep leaves tender and abundant.
• Cold damage: it blackens in a chill. Keep it warm and never set plants out until nights stay above 50F.
• Damping off: seedlings collapse at the soil line in cool, damp, still air. Sow in fresh mix, give airflow and bright light, and avoid overwatering.
• Yellowing leaves: usually overwatering or poor drainage. Let the top inch of soil dry between waterings and grow in well-drained soil.
• Leggy seedlings: too little light. Grow in full sun or under bright grow lights and pinch the tips to encourage bushy growth.