Basil (Ocimum basilicum) is a tender annual herb that suffers below about 10 °C and is killed by frost. Sow in March or April on a warm windowsill, pressing the seeds onto the surface of moist compost and keeping them at 20–25 °C. Plants should only go outside after mid-May, into a sunny, sheltered bed or pot with light, fertile soil; a greenhouse or a balcony against a warm wall gives the best results in cool summers. Water in the morning at the base, as cold wet leaves and waterlogged roots encourage grey mould and fusarium wilt. Pick the tips just above a pair of leaves rather than stripping single leaves; this makes the plant bushy. Pinch out flower buds to keep the leaves tender and aromatic. Basil loses much of its flavour when dried – freeze it chopped in oil or turn it into pesto instead. It grows well alongside tomatoes.