Basil hates the cold, so give it warmth, sun and regular pinching

Basil is easy once you accept one thing: it hates the cold. Sow it indoors from about six weeks before your last spring frost, keep it warm, and don’t put it outside until two weeks after the last frost, when the nights have warmed up. Then pinch it often.

Most failures come from rushing it out into chilly May nights, or from watering it into a soggy pot.

Sowing

Basil seed is small and germinates best at around 20 to 25 °C (68 to 77 °F).

1. Sow thinly on the surface of seed compost and cover with about 0.5 cm (¼ in) of compost or vermiculite.
2. Keep the pot somewhere warm, such as a propagator or a warm windowsill.
3. Seedlings appear in about a week. Give them as much light as you can.
4. When they have two pairs of true leaves, pot them on singly, or in small clumps of three or four.

Indoor sowings can run until about two weeks after the last frost. From two weeks after the last frost until about eight weeks after, you can also sow straight into warm soil outside.

Planting out

Wait until two weeks after your last frost, and until nights stay above about 10 °C (50 °F). Harden plants off for a week first.

• In the ground: 20 cm (8 in) apart in rows 30 cm (12 in) apart, or four to a square in square foot gardening.
• In pots: one plant per 15 to 20 cm (6 to 8 in) pot, or several in a trough.
• In a greenhouse: basil grows very well here, and it’s a classic partner for tomatoes, peppers and chillies.

Choose the sunniest spot you have. In cool, wet summers, basil often does better in a pot by a warm wall or under glass than in open ground.

Pinching and picking

Once plants are about 15 cm (6 in) tall, pinch out the growing tip just above a pair of leaves. Two new shoots grow from that point. Keep doing this every week or two, and the plant becomes a bush rather than a single stalk.

Pick from the top, never just the bottom leaves. That way every harvest is also a pinch. The first leaves are ready about 50 to 70 days from sowing, or three to five weeks after planting out.

Take off flower buds as soon as they appear. A plant left to flower stops making new leaves.

Watering and feeding

Water in the morning, at the base, and let the top of the compost dry a little between waterings. Basil left wet overnight is prone to rot and fungal disease.

Plants in pots benefit from a liquid feed every couple of weeks in summer. Ground-grown basil rarely needs feeding.

The end of the season

Basil keeps cropping until about two weeks before the first autumn frost, when cool nights blacken the leaves. Before then, pick everything that’s left and freeze it, or turn it into pesto. A pot or two can come indoors to a sunny windowsill and crop a little longer.

Varieties

Sweet or Genovese basil is the one for pesto and tomatoes. Thai basil has a hint of aniseed and copes better with heat. Greek basil makes small, compact bushes that suit pots. Purple basils look lovely but are often slower growing.

Basil pairs well with tomatoes in the companion planting guide. Set your own frost dates on the basil page to turn these windows into calendar dates.