Photo: "Basilic Thaï Siam" by Serres Fortier · CC BY 2.0

Herb · Annual-culinary

Thai Basil

Open-pollinated · Lamiaceae

Distinct from Genovese — anise/licorice flavor, NOT interchangeable in recipes. Essential in Thai, Vietnamese, and Taiwanese cuisines. More heat-tolerant, slower to bolt, and flowers have less negative impact on leaf quality than Genovese. Purple stems and flower clusters add ornamental value. Notably better downy mildew tolerance. Top basil recommendation for humid eastern climates. 'Everleaf Thai Towers' from Johnny's is a standout compact, bolt-resistant variety.

At a Glance

Days to Maturity

60–65 days

Sun

6+ hours

6-8 hours

Spacing

12–15 "

Seed Start

6–8 weeks

before transplant

Container

Yes

1+ gallon pot

Height

1–1.5 ft

Zone Planting Guide

Your USDA Zone:

Growing Guide

Germination

Germination Time 5–10 days

Optimal Temp 80°F

Seed Depth 0.25"

Transplanting

Min Soil Temp 70°F

Harden Off 7 days

Watering

Weekly Water 1–1.5 "

Needs Consistent

Method Base watering.

Soil

pH Range 6–7

Soil Type Rich, moist, well-drained

Resilience

Heat: Moderate-high Cold: Low Drought: Low

Common Problems

basil-downy-mildew

Cause: Same pathogen but Thai basil is more tolerant.

Prevention: Standard practices. Less urgent than for Genovese.

bolting

Cause: Slow-bolting. Flowers less damaging.

Prevention: Pinch for bushier growth but not critical for flavor maintenance.

Nutrition

Feeding Intensity Moderate feeder

Recommended Recipes Compost tea, Worm castings topdress

Harvest

Stems with mature leaves. Anise/licorice aroma when rubbed. Purple stems.

Storage 7 days — Stems in water on counter.

Companion Planting

Good Companions

Thai hot pepper Natural culinary pairing. Similar growing conditions.

Roma vf tomato Classic companion.

Avoid Planting Near

Common sage Different water needs.

Sources

seed_catalog Johnny's — Everleaf Thai Towers university Rutgers — Basil DM Resistance

More Herbs

Thai Basil Planting Dates by Zone

Planting dates for Thai Basil vary by USDA hardiness zone. Select your zone below for frost dates, start-indoors timing, and a full monthly planting calendar.

Zone 5A Zone 5B Zone 6A Zone 6B Zone 7A Zone 7B Zone 8A Zone 8B Zone 9A Zone 9B

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