How to Grow Purple Basil Siam Queen

Purple Basil Siam Queen

Ocimum basilicum var. thyrsiflorum

herb

Siam Queen is a striking Thai basil variety with deep purple flowers and stems, featuring a complex spicy-anise flavor profile that's essential in Southeast Asian cuisine. This ornamental herb grows as a compact, bushy plant reaching 12-18 inches tall and is both beautiful and highly productive. The leaves and flowers are edible and offer a more sophisticated taste than sweet basil, with notes of licorice and pepper.

Growing Conditions

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Sun: Full sun, 6-8 hours daily minimum; 8+ hours preferred for best flavor and flowering

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Water: Keep soil consistently moist but not waterlogged; water when top inch of soil is dry. More frequent watering needed in hot weather and containers. Avoid overhead watering to prevent fungal issues.

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Spacing: 12-18 inches

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Days to maturity: 60-75 days to first flowering

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Planting depth: Surface sow or lightly cover seeds (1/8 inch); needs light to germinate

Soil

Type: Well-draining loamy soil

pH: 6.0-7.0

Amendments:

Compost Peat moss or coco coir Perlite for drainage

Growing Zones

Find your zone →

Thrives in zones 10-11; can be grown as a summer annual in cooler zones

9b 10a 10b 11a 11b

Growth Stages

Seedling

2-3 weeks

Tiny green cotyledons emerge; first true leaves appear within 1-2 weeks with characteristic basil shape

Keep soil moist but not soggy; provide bright light; maintain warmth (70-75°F); thin seedlings to proper spacing

Vegetative

3-4 weeks

Plant develops multiple stems with oval, slightly textured green leaves; compact, bushy form establishes

Pinch off flower buds to encourage leaf production and bushier growth; fertilize every 2-3 weeks with balanced fertilizer; ensure 6+ hours of direct sun

Pre-flowering

2-3 weeks

Stems begin to show purple coloring; leaves remain green but plant energy shifts toward reproductive growth

Allow some flower buds to develop for ornamental effect if desired; continue pinching some buds to balance leaf and flower production

Flowering

4-8 weeks (continuous in warm climates)

Distinctive deep purple flower spikes emerge at stem tips; flowers are tubular and very attractive; plant is at peak ornamental and culinary value

Harvest flowers regularly for use in cooking and to encourage continued blooming; deadhead selectively; increase watering during flowering

Seed maturation

3-4 weeks after flowering

If flowers are left unpicked, small black seeds develop inside the calyx; plant may slow leaf production

Allow some flowers to set seed if you want to save seeds for next season; keep plant healthy with regular watering and feeding

Companion Planting

Plan your garden →

Plant with:

Thyme Oregano Chamomile Marigold Tomato Pepper Eggplant Mint

Avoid planting near:

Rue Sage Cabbage

Common Pests

Hand-pick in early morning; use neem oil spray; apply row covers on young plants
Increase humidity; spray with water to dislodge; use neem oil or insecticidal soap; ensure good air circulation
Spray with strong water stream; use insecticidal soap; apply neem oil; encourage beneficial insects
Use yellow sticky traps; spray with neem oil or insecticidal soap; maintain good air circulation
and
Hand-pick at dawn/dusk; use copper tape barriers; apply diatomaceous earth; remove leaf litter

Uses

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Thai Cuisine & Asian Cooking

Culinary

Siam Queen is essential in Thai cooking, used fresh in curries, stir-fries, and pad thai. The distinctive spicy-anise flavor is irreplaceable in authentic Southeast Asian dishes and complements coconut milk-based recipes beautifully. [source]

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Edible Flowers & Garnish

Culinary

The striking purple flowers are entirely edible and add visual drama to salads, cocktails, and desserts. The flowers have a milder flavor than the leaves but retain the characteristic spicy-licorice notes. [source]

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Traditional Herbal Medicine

Medicinal

Thai basil has been used in traditional Southeast Asian medicine for digestive support, anti-inflammatory properties, and respiratory health. Contains compounds like methyl cinnamate and eugenol with potential antimicrobial benefits. [source]

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Ornamental Garden Plant

Household

The deep purple flowers and stems make Siam Queen a beautiful ornamental herb suitable for borders, containers, and cut flower arrangements. Its compact bushy habit makes it ideal for patio and balcony gardens. [source]

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Fresh & Dried Herb Storage

Culinary

Leaves dry well and retain flavor for teas and cooking blends. Can be frozen in oil or dried for winter use, making it versatile for year-round cooking. [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 and flower buds once plant is 6 inches tall by pinching off the top 2 pairs of leaves. Regular harvesting promotes bushier growth and more productivity. Harvest in the morning after dew dries for best flavor. The entire purple flower spike is edible and adds both flavor and visual appeal to dishes. Continue harvesting throughout the growing season; plants remain productive for 2-3 months or longer in warm climates.

Fun Facts

🌱 Siam Queen was developed in Thailand and won an All-America Selections award in 1997 for its ornamental beauty and culinary excellence, making it a relatively modern cultivar.
🌱 Unlike sweet basil, Thai basil varieties like Siam Queen can tolerate warmer conditions without bolting as quickly, making them ideal for hot-climate gardening.
🌱 The purple pigmentation in the flowers and stems comes from anthocyanins, the same antioxidant compounds found in blueberries and red wine, which may contribute to the plant's traditional medicinal uses.

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