Italian Large Leaf Basil

Plant overview

Italian Large Leaf Basil (Ocimum basilicum) is a productive sweet basil variety valued for its large, aromatic leaves and rich flavor. It thrives in warm conditions with plenty of sunlight, fertile well-drained soil and consistent moisture. The leaves can be harvested regularly for fresh cooking, pesto, sauces and other dishes. Pinching the growing tips and harvesting often encourages branching and produces a fuller, bushier plant. In Thailand, basil can be grown year-round, but good airflow and drainage are especially important during hot, humid and rainy periods.

Quick facts

Climate & growing season

Warm tropical to subtropical climate; grows best around 20–30°C. Well suited to Thailand and can be grown year-round with adequate sunlight, consistent moisture, good drainage and airflow.

Thrives in warm, humid Thai weather. Protect from heavy monsoon rain that can compact leaves and invite fungal spots.

Seed starting

Sow seeds about 1/4 inch deep in a moist, fine seed-starting mix. Keep the medium warm and evenly moist but not waterlogged. Seeds usually germinate in about 5–10 days. Once seedlings emerge, provide plenty of bright light to encourage compact, healthy growth.

Transplanting

Transplant seedlings when they have several true leaves and are strong enough to handle. Harden them off gradually for about 5–7 days before moving outdoors. Transplant into well-drained soil, water thoroughly after planting and avoid transplanting during the hottest part of the day.

Sunlight

Italian Large Leaf Basil grows best with about 6–8 hours of sunlight daily. Plenty of light encourages strong, compact growth and flavorful leaves. In extremely hot weather in Thailand, morning sun with light afternoon shade can help prevent heat stress and leaf scorching.

Watering

Water regularly to keep the soil evenly moist, especially during active growth. Allow the top layer of soil to begin drying before watering again. Avoid both prolonged dryness and waterlogged soil. Water near the base of the plant when possible and ensure good drainage during Thailand's rainy season.

Soil & growing medium

Grow Italian Large Leaf Basil in fertile, loose, well-drained soil rich in organic matter. A soil pH around 6.0–7.5 is suitable. Compost can be added before planting to improve fertility and moisture retention, but the soil should still drain freely to prevent root problems.

Fertilizing

Italian Large Leaf Basil benefits from moderate feeding because it is harvested regularly for its leaves. Add compost or organic matter before planting, then apply a diluted balanced or organic fertilizer every 3–4 weeks during active growth. Avoid excessive fertilizer, which can produce overly soft growth and may reduce leaf flavor and aroma.

Growth timeline

1. 1
   Stage 1

   Sowing

   Day 0

2. 2
   Stage 2

   Germination

   Day 5–10

3. 3
   Stage 3

   Seedling

   Day 10–25

4. 4
   Stage 4

   Transplant

   Day 25–30

5. 5
   Stage 5

   First pinch harvest

   Day 45–60

Harvesting

Begin harvesting once the plant is well established and has several sets of healthy leaves. Cut stems just above a pair of leaves to encourage new side branches and a bushier plant. Harvest regularly and pinch off flower buds if growing primarily for leaves. Avoid removing more than one-third of the plant at one time.

Pests & diseases

Whitefly and slugs are the main issues. Rinse leaves with a gentle spray and pick pests off in the morning.

Frequently asked