Thai basil

Sun

Full sun; light afternoon shade is useful in very hot climates.

Water

Keep evenly moist but not waterlogged; water when the soil surface begins to dry. Containers may need daily checks in hot weather.

Soil

Fertile, well-drained soil enriched with compost; use a free-draining potting mix in containers.

Height

1-2.5 ft (0.3-0.75 m)

Spread

1-1.5 ft (0.3-0.45 m)

Flowers

Pink to purple flowers on dark purple spikes from summer into autumn if not regularly pinched out.

Foliage

Aromatic, green, pointed leaves with lightly toothed edges, usually carried on purple stems.

Growth

Fast in warm weather

Care needed

Low

• Pollinators
• Heat tolerant
• Low allergen
• Fragrant
• Edible

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Needs looking after

Pick your zone, country, light and whether you have pets.

1. Planting day

   0.5 ft (0.15 m)

2. After 1 year

   1.7 ft (0.53 m)

   full size

Full size in one season.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Growth rate

Fast

• Plant out only after frost risk has passed and nights are consistently above 10°C.
• Space plants about 1-1.5 ft (0.3-0.45 m) apart to allow air movement.
• Water at soil level, keeping the root zone moist without leaving pots standing in water.
• Mix compost into beds before planting; feed container plants lightly with a balanced liquid fertiliser according to its label.
• Apply a light mulch once the soil is warm, keeping it away from the stems.

Pruning. Pinch out the growing tips once plants have several pairs of true leaves, cutting just above a leaf pair to encourage branching. Remove developing flower spikes for continued leafy growth, or leave a few for pollinators.

Begin picking when plants are well established and have several pairs of full-sized leaves, usually about 6-8 weeks after sowing in warm conditions. Snip leafy shoot tips just above a leaf pair, taking no more than about one-third of the plant at a time; young leaves are tender and strongly aromatic.

Early spring

Sow indoors in warmth, about 6-8 weeks before your expected planting-out date.

Late spring

Harden plants off gradually, then plant outside after frost risk has passed and nights are consistently warm.

Early summer

Pinch growing tips to encourage bushy plants and begin light harvesting.

Summer

Harvest regularly, check container moisture and remove unwanted flower spikes.

Late summer

Leave selected flower spikes for insects or seed collection; continue picking leafy shoots elsewhere.

Autumn

Harvest remaining leaves before cold weather; freeze surplus leaves and remove plants killed by frost.

• Plant beside paths in a kitchen garden so aromatic leaves are within easy reach.
• Group in patio containers with chillies for contrasting foliage, purple stems and edible crops.
• Use repeated clumps along the front of vegetable beds to give productive planting a tidy edge.
• Allow a few plants to flower among calendulas and other edible-garden flowers for pollinator interest.

Garden styles it suits: Potager (kitchen garden), Herb parterre, Edible landscape, Sensory garden, Small-space and Tropical.

Plant it with: Tomatoes, Chillies, Sweet peppers, Lemongrass, Calendulas and French marigolds.

Wildlife: Flowers provide nectar and pollen for bees and other visiting insects. Regularly removing all flower spikes reduces this value.

• Slugs and snails can strip young plants: inspect after dark, remove pests and protect vulnerable seedlings.
• Aphids gather on soft shoot tips: wash them off with water and encourage ladybirds and other predators.
• Basil downy mildew causes yellow patches above leaves and grey-purple growth beneath: remove affected plants, avoid wetting foliage and improve spacing.
• Cold, wet soil causes stalled growth and root rot: delay planting until conditions are warm, improve drainage and empty standing water from saucers.

Not known to be toxic to people, cats, dogs or horses. Leaves and flowers are edible in normal culinary amounts; concentrated essential oil is not equivalent to eating the herb and should not be given to pets.

• Sweet basil (Ocimum basilicum)

  Typical sweet basil has broader, softer leaves and a sweeter, less distinctly anise-like scent; Thai basil usually has narrower leaves and conspicuous purple stems.

• Holy basil (Ocimum tenuiflorum)

  Holy basil usually has hairier leaves and stems, more strongly toothed leaf edges and a clove-like, peppery aroma rather than Thai basil's anise scent.

• Lemon basil (Ocimum × africanum)

  Crushed leaves smell distinctly of lemon rather than anise; flowers are usually white and stems are generally greener.

The common name refers to its prominent use in Thai cooking, while the botanical epithet thyrsiflora refers to its clustered flower spikes.

Propagation. Sow seed shallowly indoors at about 20-25°C, or directly outdoors once soil and nights are reliably warm. Soft, non-flowering shoot cuttings also root readily in water or moist potting mix.

Accepted botanical name

Ocimum basilicum basilicum Ocimum basilicum var. thyrsiflora is an older name for Ocimum basilicum basilicum.

Sources: GBIF (CC BY 4.0). The care and design notes are LandscapeGPT's own.