How to Grow Thai Giant Basil
Wikimedia Commons
Thai Giant Basil
Ocimum basilicum var. thyrsiflorum
herbThai Giant Basil is a robust cultivar of sweet basil with large, textured leaves and a distinctive anise-like flavor with subtle licorice notes. It grows taller and more vigorously than common basil varieties, reaching 2-3 feet in height, and produces attractive purple flowers ideal for both culinary and ornamental purposes.
When should you plant Thai Giant Basil in your zone?
Get a personalized planting timeline — when to start seeds, transplant, and harvest — based on your USDA zone and local frost dates. Free to start.
Example Thai Giant Basil timeline · Pittsburgh, PA (Zone 6b)
-
Plant Thai Giant Basil
Around Apr 17Near Pittsburgh's average last spring frost.
-
Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
-
Harvest Thai Giant Basil
Around Jun 16≈ 60 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Thai Giant Basil dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 10-11, can be grown as annual in zones 3-9
Sign up free to see if Thai Giant Basil grows in your zone — and get a personalized planting timeline.
Get my Thai Giant Basil timeline →Growth Stages
Seedling
2-3 weeksTiny cotyledons emerge, followed by first true leaves. Plant appears delicate and low-growing.
Keep soil moist, provide bright light (grow lights if indoors), maintain 70-75°F. Thin seedlings to proper spacing once true leaves develop.
Vegetative
3-4 weeksRapid stem and leaf growth. Plant develops thick stems and increasingly large, textured leaves. Growth is vigorous and bushy.
Pinch top growing tips regularly to encourage branching and bushiness. Maintain consistent moisture and feeding with balanced fertilizer every 2-3 weeks. Ensure excellent air circulation.
Pre-flowering
2-3 weeksPlant reaches mature height (2-3 feet). Flower buds form at stem tips, visible as dark purple elongated structures.
Continue pinching spent flower buds to extend leaf production if harvesting for culinary use. Reduce nitrogen fertilizer slightly to balance growth.
Flowering
4-6 weeksBeautiful purple flower spikes emerge from terminal growth points. Flowers are fragrant and attractive to pollinators.
Harvest flowers for culinary use or allow to remain for ornamental appeal. Deadhead regularly to prevent excessive seed set and extend plant life.
Seed Production & Decline
3-4 weeksIf left unharvested, flowers develop seeds in brown capsules. Plant vigor may decline as energy shifts to reproduction.
Allow some flowers to mature if saving seeds, otherwise remove spent flowers. Plant typically begins to decline in late fall/winter in most climates.
Common Pests
-
Spray with water to dislodge, use neem oil or insecticidal soap, increase humidity, improve air circulation
-
Spray with strong water stream, use insecticidal soap, apply neem oil, encourage beneficial insects like ladybugs
-
Remove affected leaves, use yellow sticky traps, apply neem oil or spinosad, improve air circulation
-
Hand-pick in early morning, use row covers on young plants, apply neem oil, use pheromone traps away from plants
-
and
Remove by hand at night, use copper barriers, diatomaceous earth, beer traps, encourage ground beetles
Uses
Thai Cuisine & Stir-fries
CulinaryThai Giant Basil's distinctive anise and licorice flavors make it essential in Thai cooking, particularly in stir-fries, curries, and pad krapow (basil stir-fry with meat). The large leaves are perfect for tearing into dishes or using whole as wraps. [source]
Infusions & Tea
CulinaryFresh or dried leaves can be steeped into aromatic herbal tea with warm, spiced notes. The flowers are also edible and add visual appeal to beverages and dishes. [source]
Anti-inflammatory & Digestive Support
MedicinalThai basil contains eugenol and other compounds with anti-inflammatory and antimicrobial properties traditionally used in Southeast Asian medicine to support digestion and reduce inflammation. [source]
Natural Pest Deterrent
HouseholdGrow Thai Giant Basil near doors and windows or dry and place around the home to naturally repel flies, mosquitoes, and other insects due to its strong aromatic volatile oils. [source]
Garden & Container Ornament
OrnamentalThe tall stature (2-3 feet), textured large leaves, and purple flower spikes make Thai Giant Basil an attractive ornamental specimen for containers, borders, and mixed herb gardens. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Begin harvesting leaves when plant is 6-8 inches tall by pinching off top 2-3 leaf pairs. Harvest regularly to encourage bushiness and delay flowering. Best flavor is in morning after dew dries. Pinch flower buds to extend leaf production. Can harvest continuously throughout the growing season. For maximum yield, harvest before flowers fully develop.
Fun Facts
- 🌱 Thai Giant Basil is sometimes called 'Holy Basil' in English, though true holy basil (Tulsi) is a different species (Ocimum tenuiflorum) with different flavor and medicinal properties.
- 🌱 The purple color of the stems, leaves, and flowers is due to anthocyanin pigments, the same compounds that give blueberries and red wine their color and antioxidant benefits.
- 🌱 Thai basil's distinctive anise flavor comes from anethole, the same volatile compound found in anise seeds and fennel, making it instantly recognizable in authentic Thai cuisine.
Gardening Terms
New to gardening? Learn about terms used in this guide:
Join 30,000 gardeners planning their gardens with LizPlants.
Get your personalized Thai Giant Basil planting timeline
Tell us your zip code and we'll calculate exactly when to start Thai Giant Basil seeds, transplant seedlings, and harvest — based on your USDA zone and local frost dates. Includes calendar reminders and printable task lists. Free to start.
Get my Thai Giant Basil timeline →