How to Grow Siam Queen Basil
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Siam Queen Basil
Ocimum basilicum var. thyrsiflora
herbSiam Queen is a compact, bushy Thai basil variety prized for its intense anise-licorice flavor and ornamental purple flowers. It grows as an annual herb in most climates and produces abundant aromatic foliage ideal for Asian cuisine. This cultivar is more cold-tolerant than many Thai basil varieties and flowers prolifically.
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Example Siam Queen Basil timeline · Pittsburgh, PA (Zone 6b)
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Plant Siam Queen Basil
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Siam Queen Basil
Around Jun 6≈ 50 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Siam Queen Basil dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Zones 3-11 as an annual; perennial in zones 10-11
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Seedling
2-3 weeksTiny seedlings emerge with rounded cotyledons; true leaves develop within 1-2 weeks
Maintain consistent moisture and warmth (70-75°F). Provide bright light to prevent legginess. Thin seedlings to proper spacing or transplant to individual pots.
Vegetative Growth
3-5 weeksBushy plant develops multiple stems with oval, aromatic green leaves; compact habit with no flowers yet
Pinch off flower buds to encourage leaf production and bushier growth. Water regularly and fertilize every 2-3 weeks with balanced fertilizer. Begin harvesting outer leaves once plant is 6-8 inches tall.
Flowering
4-8 weeks (ongoing)Dense purple or dark magenta flower spikes emerge at stem tips; plant becomes more ornamental
Flowers are edible and attractive; leave some for pollinators if desired. Continued pinching extends leaf production. Regular harvesting of stems extends vegetative phase.
Peak Production
6-12 weeksPlant is full and robust with continuous flowers and harvestable foliage throughout growing season
Harvest frequently (every 3-4 days) to maintain bushy shape and delay excessive flowering. Keep soil consistently moist during hot weather. Deadhead spent flowers to redirect energy to leaves.
Decline/Frost Sensitivity
Until frost (variable)Plant slows as temperatures drop below 50°F; foliage becomes less vigorous; frost kills plant
Harvest remaining leaves before first frost. Collect seeds from mature flowers for next season if desired. In mild climates, may overwinter indoors.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Hand-pick in early morning; use neem oil or insecticidal soap; row covers for young plants
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Spray leaves with water to dislodge; increase humidity; use neem oil or miticide if severe
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Yellow sticky traps; insecticidal soap; neem oil; reflective mulch to confuse adults
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Strong water spray; insecticidal soap; neem oil; encourage beneficial insects like ladybugs
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Use disease-resistant varieties; improve drainage; remove infected plants; avoid overhead watering
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Improve air circulation; avoid wetting foliage; use copper fungicide; remove infected leaves
Uses
Thai & Southeast Asian Cooking
CulinarySiam Queen basil is essential in Thai cuisine, lending its distinctive anise-licorice flavor to curries, stir-fries, and pad thai. The flowers are also edible and add visual appeal to dishes. [source]
Tea & Infusions
CulinaryFresh or dried leaves create an aromatic herbal tea with a warm, licorice-like quality. Steep 5-10 leaves in hot water for a soothing beverage. [source]
Traditional Medicine & Digestion
MedicinalThai basil has been used in traditional medicine to support digestion, reduce inflammation, and provide antimicrobial benefits. The essential oils contain compounds like estragole and linalool with documented bioactivity. [source]
Aromatic & Insect Repellent
HouseholdThe powerful fragrance naturally repels mosquitoes and flies, making it valuable for patio plantings or dried arrangements. Dried bundles can scent a room naturally. [source]
Cut Flowers & Garden Ornament
CraftThe showy purple flower spikes make Siam Queen an attractive ornamental herb for flower arrangements and garden displays. Fresh or dried flowers add color and texture to crafts. [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 when plant reaches 6-8 inches tall by pinching off leaf clusters from the top. Harvest regularly every 3-4 days to encourage bushiness and extend the vegetative stage. Pinch off flower buds to maximize leaf production, or allow some flowers for ornamental appeal and edibility. Harvest in the morning after dew dries for best flavor. Cut stems just above a leaf node to encourage branching. Siam Queen produces continuously from mid-summer through first frost.
Fun Facts
- 🌱 Siam Queen was selected specifically for its superior cold tolerance compared to other Thai basil varieties, making it more reliable in temperate gardens.
- 🌱 The flowers are fully edible with the same anise flavor as the leaves and make a striking purple garnish for Thai and Asian dishes.
- 🌱 Basil is believed to have originated in India and was sacred in Hindu tradition; the name comes from the Greek word 'basileus' meaning 'king.'
Gardening Terms
New to gardening? Learn about terms used in this guide:
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