Thai Basil Herb Seeds

Thai Basil is a frost-tender annual herb that thrives in warm weather. Grow it in full sun, fertile well-drained soil and consistent moisture for a regular supply of aromatic leaves.

Quick Start

• Sowing season: Spring to summer after frost
• Sowing depth: 2–5mm
• Germination: 5–10 days
• Best germination temperature: approximately 20–30°C
• Plant spacing: 25–30cm
• Position: Full sun
• Mature height: approximately 50–80cm
• Maturity: approximately 50–70 days
• Harvest: begin light picking once plants are established

Sowing

Thai Basil can be direct sown or raised as seedlings.

For direct sowing:

1. Prepare fertile, well-drained soil.
2. Wait until frost risk has passed and the soil has warmed.
3. Sow approximately 2–5mm deep.
4. Keep the soil evenly moist during germination.
5. Thin seedlings once established.

For seedling raising:

1. Fill trays or small pots with fine seed-raising mix.
2. Sow approximately 2–5mm deep.
3. Keep warm and consistently moist.
4. Provide bright light after germination.
5. Transplant outdoors once seedlings are established and conditions are reliably warm.

When to Sow

For most Australian climates, sow during:

Spring through summer

General guidance:

• Cool climates: spring to early summer
• Temperate climates: spring through summer
• Subtropical climates: late winter or spring through summer where frost risk is low
• Tropical and frost-free climates: a broader sowing period is possible, avoiding severe heat or prolonged wet-season humidity where necessary

Thai Basil is sensitive to frost and cold soil.

Germination

Expect germination in approximately:

5–10 days

For reliable propagation, aim for approximately:

20–30°C

The seed can germinate across a broader temperature range, but warm conditions generally provide more reliable establishment.

Position & Spacing

Grow in:

Full sun

Aim for around 6–8 hours of direct sunlight daily where practical.

Allow approximately:

25–30cm between plants

More space can be provided where larger, freely branching plants are desired.

In very hot conditions, some protection from harsh late-afternoon sun can benefit container-grown plants.

Watering

Keep the soil consistently moist but not waterlogged.

For garden-grown plants:

• water thoroughly when the upper soil begins to dry;
• direct water towards the root zone;
• avoid repeatedly soaking the foliage;
• mulch established plants where useful to conserve moisture.

For pots:

• check moisture more frequently during hot weather;
• water thoroughly when required;
• ensure excess water drains freely;
• do not leave containers standing permanently in water.

Avoid repeated severe wilting, which can reduce growth and encourage premature flowering.

Feeding

Thai Basil performs best in fertile soil.

Before planting, incorporate mature compost or another suitable soil amendment where required.

Container-grown plants can be fed periodically during active growth according to the fertiliser manufacturer's directions.

Pinching & Harvesting

Once plants have several established sets of leaves:

1. Find a healthy pair of leaves.
2. Cut or pinch the stem immediately above them.
3. Allow the two side shoots below the cut to develop.
4. Repeat regularly as the plant grows.

This encourages bushier growth and more harvestable stems.

Begin light harvesting once plants are established rather than waiting for full maturity.

Managing Flowers

Thai Basil produces attractive purple to lavender flower spikes.

If fresh leaves are the priority, pinch off developing flower spikes before flowering becomes extensive.

Leave selected flowers if you want ornamental blooms, pollinator activity or eventual seed production.

Growing Thai Basil in Pots

Thai Basil grows well in containers.

For one established plant, use a pot approximately 20–30cm wide or larger with:

• good drainage holes;
• quality potting mix;
• a warm sunny position; and
• regular watering.

One well-developed plant per medium-sized pot generally provides better airflow than overcrowding several plants together.

Succession Sowing

For a longer supply of young plants, sow smaller batches approximately every:

3–4 weeks

during suitable warm weather.

Other Basil Varieties

For broad leaves and classic pesto use, see Large Leaf Sweet Basil Herb Seeds.

For a milder sweet basil with compact growth, see Sweet Green Basil Herb Seeds.

Harvest & Storage

Harvest healthy young leaves and tender stems as required.

Thai Basil is best used soon after picking for maximum aroma.

Avoid prolonged storage at very low temperatures because basil foliage can darken and suffer chilling injury.

Leaves can also be frozen or dried, although the flavour changes compared with fresh Thai Basil.

Seed Storage

Store unused seed sealed in a cool, dry and dark place away from heat, moisture and direct sunlight.