When can I sow basil seed in the UK?

Indoors from late April to mid-May; in a heated propagator from late March. Don't sow outdoors except on a sheltered south-coast bed in late May. Basil seedlings need 18°C minimum and hate cold wet soil — sowing too early gives leggy, stalled plants. Two or three pots indoors gives a household plenty.

Can I grow basil outdoors in the UK?

Only in pots, in a sunny sheltered south-facing position, from June to early September. The UK summer is borderline for basil — a cool wet July checks growth and a chilly August night below 10°C halts it. Greenhouse, polytunnel, or warm windowsill basil is more productive than outdoor in most of the UK.

Why is my basil bolting (flowering)?

Long days, heat stress, or the plant is mature. Bolting is normal — basil is an annual that's trying to set seed before frost. Pinch out the flower spikes as soon as they appear; this delays bolting by a few weeks. After several rounds of pinching, the plant will eventually flower regardless — that's the end of its useful life. Start a fresh sowing every 6 weeks if you want continuous supply.

What's the difference between sweet, Thai, and lemon basil?

Sweet (Genovese) is the standard pizza-and-pesto basil — broad leaves, classic basil flavour. Thai basil has smaller pointed leaves and a stronger aniseed note; the right basil for pho and Thai curries. Lemon basil has narrower leaves and a citrus-floral flavour; works in dressings and fish dishes. Sweet is the everyday; the others are worth a separate pot if you cook with them often.

How do I store fresh basil?

Treat cut stems like a small bouquet — stand in a glass of cold water on the kitchen counter, not in the fridge (cold blackens basil leaves). It keeps 4–5 days. For longer storage, blend whole leaves with olive oil and freeze in ice-cube trays. Drying ruins the flavour; freezing in oil preserves it.

Can I grow basil from supermarket pots?

Yes — the multi-stemmed pots at supermarkets are bunches of seedlings crammed together, struggling for root space. Tip the pot out, gently tease the seedlings apart, and pot them on individually (or in groups of 2–3) in fresh compost. Place on a sunny windowsill. Within two weeks they double in size and stop dying back.

Sweet basil

Ocimum basilicum

herb☀️ full-sun🪴 well drained, rich📏 small🌡️ RHS H1c

📋Quick Facts

Height

0.5-0.6m

Spread

0.3-0.4m

About

Sow basil seed indoors from late April to mid-May; don't bother with outdoor sowings except on a sheltered south-coast windowsill. Basil is very frost-tender (RHS H1c) and hates cold wet soil — even a chilly summer night below 10°C checks growth. Grow in 1-litre pots on a sunny windowsill, in a greenhouse, or in a polytunnel; outdoor plants only thrive in pots in a sheltered south-facing position from June to early September. Pinch out flower spikes as they appear to keep the plant leafy. Pick young leaves regularly from the top; older leaves get bitter. Sweet (Genovese) basil is the kitchen standard; Thai basil for South-East Asian dishes; lemon basil for Mediterranean.

Top tip

Basil loves warmth, rich soil and regular picking; pinch out tips often to keep plants bushy and leafy.

Also known as: Basilico dolce, Gewone basilicum, Manjericão, Albahaca, Sweet basil, Basilic (basilic doux), Ocimum basilicum, Bazylia słodka

How to grow sweet basil

1
Sow seed
Late April to mid-May. 9 cm pots of multi-purpose compost, 5–6 seeds per pot, lightly covered. 18–22°C on a warm windowsill or in a propagator. Germination in 7–14 days.
2
Thin to the strongest
Once seedlings are 5 cm tall, thin to 2–3 per pot. Don't transplant — basil hates root disturbance.
3
Pot on or plant in containers
Pot on to a 2-litre pot when roots fill the smaller, or plant 3 seedlings per 30 cm container. Outdoors only after the last frost in a sheltered sunny position.
4
Water carefully
Water at the base in the morning. Basil hates wet leaves and waterlogged roots — let the compost surface dry between waterings.
5
Pinch out flowers
As soon as flower spikes appear, pinch them out. Flowering shuts down leaf production. Keep doing it through the season.
6
Pick from the top
Pick the top pairs of leaves regularly; the plant branches at each cut and produces more. Don't strip the lower leaves; they keep the plant alive.
7
Move under cover in autumn
From mid-September, night temperatures drop below basil's tolerance. Move pots indoors to extend the season to October or November.

Common questions

Pest Resilience

2/5 — Somewhat vulnerable

Prone to aphids, slugs, and downy mildew; needs warmth and good airflow.

Companion Planting

Grows well with

Pepper Tomato

Keep apart from

Sage Rosemary

Visual Characteristics

🍳

Culinary

Culinary Use

Pesto, pasta sauces, caprese salad, pizza, bruschetta, infused oils

The sweet basil year in your garden

Dispatching imaginary bots to check your garden out...

What to do now

How to Propagate

🌰Seed

Easy

✂️Cutting

Moderate

Hardiness Zones

H1a (tender)H7 (very hardy)

H1a

H1b

H1c

RHS H1c

USDA 10–11 equivalent

Sweet basil

Sweet basil

📋Quick Facts

About

How to grow sweet basil

Common questions

Pest Resilience

Companion Planting

Visual Characteristics

The sweet basil year in your garden

How to Propagate

Hardiness Zones

Names in Other Languages(7)