How to Grow Thai Basil (Selasih) from Seed in Malaysia

Yes — Thai basil is one of the best herbs for Malaysia because it loves heat and sun, unlike many herbs from cooler countries. You can start picking leaves about 6–8 weeks after sowing, and one well-kept plant can keep producing for months. The key tip: pinch out the tips early and remove flower spikes as they appear — this keeps the plant bushy and leafy instead of tall, woody and full of seeds.

Quick facts

Item	Thai basil
Sun	Full sun, 6 hours or more; tolerates some afternoon shade
Sowing	Seedling tray; scatter on the surface and cover with 2–3 mm of fine mix
Germination	5–10 days
Spacing	25–30 cm between plants, or one plant per pot
Days to harvest	About 45–60 days for the first regular picking
Container	At least 20 cm deep and 20 cm wide per plant

Thai basil, selasih and kemangi

In Malaysia, "selasih" is used for several kinds of basil. Thai basil (the one used in Thai cooking, with purple stems and an anise-like aroma) is grown in the same way as other basils. Lemon basil, often called kemangi, is a different plant with a lemony smell. This guide covers Thai basil, but the method also works for most basils.

Choosing a spot and container

Thai basil is a heat lover. The sunniest spot on your balcony, rooftop or yard is ideal; it handles west-facing balconies better than leafy greens do, as long as the pot does not dry out. In shady spots it grows slowly, stretches, and is more prone to fungal problems.

Each plant eventually forms a small bush, so give it room: a pot or polybag at least 20 cm deep and 20 cm wide for one plant, or a long trough with plants 25–30 cm apart. Terracotta and light-coloured pots keep roots cooler than thin black pots in full sun. Drainage holes are essential.

Soil and potting mix

Basil likes fertile, well-drained soil:

• 2 parts potting mix
• 1 part compost
• 1 part burnt rice husk or coarse sand for drainage

Avoid heavy soil that stays wet. Basil roots rot quickly in waterlogged pots, especially in the rainy season.

How to sow Thai basil step by step

1. Fill a seedling tray with fine, moist seedling mix.
2. Sow 2–3 seeds per cell on the surface. Basil seeds are small and black.
3. Cover lightly with 2–3 mm of fine mix, or just press them in. When wet, basil seeds form a clear jelly-like coat — this is normal.
4. Water gently with a spray or fine rose and keep the tray in bright shade. Seedlings usually appear in 5–10 days.
5. Give full light once sprouted, starting with morning sun. Thin to one strong seedling per cell.
6. Transplant at 4–6 true leaves, about 3–4 weeks after sowing, into pots or 25–30 cm apart in a trough. Plant at the same depth and water in well.
7. Shade for a day or two after transplanting, then move into full sun.

Pinching and shaping

This is what makes the biggest difference to how much basil you harvest:

• When the plant is about 15–20 cm tall with 3 pairs of leaves, cut the top just above the second or third pair of leaves. Two new shoots will grow from that point.
• Repeat on each new shoot every couple of weeks. The plant becomes bushy with many more leaves.
• Remove flower spikes as soon as you see them. Once Thai basil flowers freely, leaf production slows and the stems become woody.

Watering in hot and rainy weather

• Hot spells: water deeply in the morning. Pots in full sun may need a second check in the late afternoon. Slight wilting at midday in full sun is normal; wilting in the morning means it is too dry.
• Rainy season: let the top 1–2 cm of soil dry between waterings. During long wet spells, move pots under the eaves and raise them off the ground. Overwatering is a more common killer of basil than drought.
• Water at the base, in the morning, so the leaves dry quickly.

Feeding

Mix compost into the potting mix at planting. Start a liquid fertilizer about two weeks after transplanting and feed every 10–14 days at the label rate. Because you are harvesting leaves regularly, a little extra compost on top of the pot every month helps keep growth going.

If you are unsure how much fertilizer to mix:

CalculatorsFertilizer Dilution CalculatorFertilizer dilution calculator: how many ml or grams of liquid or soluble fertilizer to mix for your watering can or sprayer, from ml/L or 1:N ratio.

Common problems and pests in Malaysia

• Aphids and whiteflies. Clusters on soft shoot tips and leaf undersides; whiteflies fly up when you shake the plant. Spray diluted neem oil or a mild soap solution in the evening, covering leaf undersides, and repeat every few days.
• Mealybugs. White cottony clumps in leaf joints. Wipe off with a cotton bud dipped in soapy water, then spray neem oil.
• Caterpillars and grasshoppers. Holes in leaves. Hand-pick.
• Snails and slugs. Mainly attack young transplants after rain. Hand-pick at night.
• Leaves yellowing with grey or dark fuzz underneath. A fungal leaf disease favoured by humid, crowded conditions. Remove affected leaves, space plants for airflow and water the soil, not the leaves.
• Wilting with dark, soft stems at the base. Root or stem rot from waterlogging. Improve drainage; badly affected plants rarely recover, but healthy tips can be rooted as cuttings.
• Tall, woody plant with few leaves. It has been allowed to flower. Cut back by about a third above a pair of leaves, remove all spikes and feed — new shoots usually follow.

More natural methods:

GuidesOrganic Pest Control for Malaysian Home GardensIdentify aphids, whiteflies, mealybugs, thrips, spider mites, caterpillars, leaf miners, snails and fruit flies, and control them organically and safely.

Harvesting

• Start picking when the plant is well branched, about 6–8 weeks after sowing.
• Always cut above a pair of leaves rather than pulling single leaves from the bottom. Each cut becomes two new shoots, so harvesting is the same as pinching.
• Take up to a third of the plant at a time, then let it regrow.
• Pick in the morning, when the aroma is strongest.

Thai basil is cut-and-come-again by nature: with regular picking, feeding and flower removal, one plant can keep producing for months. When it eventually becomes woody and tired, replace it with a new plant.

Saving seed and taking cuttings

Seed: let one or two flower spikes stay on a healthy plant. When the spikes turn brown and dry, cut them and leave them in a paper bag for a few days, then shake or rub out the small black seeds. Store dry in an airtight jar. Different basils can cross-pollinate when they flower near each other, so seeds from a mixed herb garden may not come true.

Cuttings: the fastest way to get a new plant. Cut a 10 cm shoot tip without flowers, remove the lower leaves and stand it in a glass of water in bright shade. Roots usually appear within one to two weeks; then plant it in a pot.

FAQ

Why is my Thai basil all stems and flowers? It needs pinching. Cut it back above a pair of leaves, remove the flower spikes, feed it and keep picking regularly.

Can I grow Thai basil indoors? It needs strong light. A very sunny window or a grow light can work, but a sunny balcony gives much better results.

Can I grow Thai basil from supermarket stems? Often, yes — fresh stems without flowers usually root in water.

Does Thai basil like the rain? It tolerates rain, but not waterlogged soil. Good drainage and raised pots are the key in the rainy season.

Watch it grow