Basil is a tender annual with fragrant leaves for pesto, pasta, salads and tomato dishes. In British summers it resents cold and persistent rain, making a bright windowsill, greenhouse or polytunnel far more dependable than an exposed border.

When and how to sow

Sow seeds in module trays from March to June, using moist potting compost and gentle warmth. Prick out seedlings when large enough to handle, then grow them in bright light. Plant outside only after the last spring frost, choosing a very warm, sheltered position. Space plants 25 cm apart in containers or rich, free-draining soil. Sweet Genovese and compact Greek basil are reliable choices.

Care

Water the compost when its surface begins to dry, without leaving pots saturated. Keep plants warm, well lit and protected from chilly nights. Pinch out growing tips regularly to make bushy plants, and remove flower buds promptly so leaves remain plentiful for cooking.

Common problems

Cold weather can blacken foliage, while overwatering and poor ventilation encourage weak growth or damping off in young seedlings. Avoid wet compost, crowded pots and cold windowsills. Raise plants in warmth, water the soil rather than leaves, and discard seedlings that collapse at the base.

Harvest

Begin picking once plants are sturdy, cutting short leafy shoots just above a pair of leaves. Frequent light harvesting encourages branching. Use leaves straight away in summer cooking, as their flavour fades quickly after cutting. Do not remove more than one third of a small plant at once.

Growing Basil: frequently asked questions

When should I sow basil in the UK?

Sow seeds in module trays from March to June, using moist potting compost and gentle warmth.

What are common problems when growing basil?

Cold weather can blacken foliage, while overwatering and poor ventilation encourage weak growth or damping off in young seedlings.

When is basil ready to harvest?

Begin picking once plants are sturdy, cutting short leafy shoots just above a pair of leaves.

General guidance for UK home gardens and allotments. Reference figures are typical values; your exact timing depends on your region, last-frost date and variety. Page updated 19 Sep 2026.