Best Fertiliser for Basil (Including Thai Basil): How to Grow Lush, Aromatic Plants

Basil is one of the most widely grown herbs in Australian gardens and kitchens. From sweet Genovese to spicy Thai varieties, this versatile herb thrives in warm conditions and benefits from consistent feeding.

Basil Varieties & Growing Conditions

Basil (Ocimum basilicum) grows quickly and is perfect for garden beds, balcony pots, and indoor herb setups. Common varieties include:

Genovese Basil: Classic sweet basil with large green leaves – ideal for pesto and salads
Thai Basil: Spicy and aromatic with purple stems – essential for stir fries and Southeast Asian dishes
Lemon Basil: Citrusy-flavoured, used in teas and desserts
Greek Globe Basil: Compact bushy variety with small leaves – great for containers

Basil prefers warm weather, full sun (6–8 hours daily), and regular water. It grows as an annual in most climates but can be grown year-round in frost-free areas.

Position: Sunny, sheltered spot
Soil: Rich, well-draining, slightly acidic (pH 6.0–7.0)
Climate: Grows best in spring and summer; protect from frost and cold wind

How to Care for Basil & Thai Basil Plants

Basil is a fast-growing herb that benefits from light, consistent care. When properly fed and pruned, it produces lush foliage all season long.

Watering & Light

Water regularly—don’t let the soil dry out completely, but avoid soggy roots
Container-grown basil needs more frequent watering, especially in summer
Provide 6–8 hours of full sun per day (or strong indoor light if grown inside)

Pruning for Better Growth

Pinch off the top pair of leaves regularly to encourage branching
Never let basil flower—remove flower spikes immediately to extend leaf growth
Harvest from the top down, not from the bottom, to maintain structure

Common Basil Issues

Yellow leaves: Often due to nutrient deficiency or poor drainage
Spindly stems: Caused by low light or overwatering
Poor flavour: Can result from low potassium or excessive nitrogen

Thai basil, in particular, benefits from regular feeding to maintain its strong aroma and upright structure, especially in pots or warm climates where growth is rapid.

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Best Fertiliser for Basil: What NPK Ratio Helps Basil Thrive?

Basil is a leafy herb that loves regular feeding but is sensitive to excessive nitrogen. The ideal fertiliser encourages strong, fragrant leaves without causing weak, overly soft growth.

What Nutrients Does Basil Need?

Moderate Nitrogen (N): Fuels green leaf growth without overstretching stems
Balanced Phosphorus (P): Supports root development and nutrient uptake
High Potassium (K): Essential for aroma, oil production, and flavour
Magnesium & Iron: Keep leaves rich in colour and prevent yellowing

Fertilising Schedule

Seedlings: Start feeding 2–3 weeks after germination using a half-strength liquid feed
Active growth phase: Feed every 10–14 days with a complete liquid fertiliser
Potted basil: May need weekly feeding due to quicker nutrient leaching
End of season: Reduce feeding to avoid bitterness in older leaves

Liquid fertilisers are ideal for basil, especially in pots. They provide fast uptake and allow you to adjust feeding strength easily. A balanced NPK formula like 20-20-20 or one slightly higher in potassium works well for most basil types.