How to grow basil

Basil is a warm-season culinary herb grown for its aromatic leaves, the backbone of pesto and a fixture in Italian, Mediterranean, and Asian cooking. Unlike hardier kitchen herbs, it holds no space in the garden outside the frost-free months; it goes in only after nights stay reliably warm and comes out at the first real cold snap, so it occupies a bed for a single warm season rather than overwintering or self-seeding into a permanent patch. Regular harvesting by pinching stem tips just above a leaf pair keeps the plant bushy and productive and delays the flowering that dulls its flavor.

The hardest part of growing basil well is basil downy mildew, a fungal disease that spreads readily in humid, crowded plantings. Pennsylvania State University Extension describes it as yellowing on the upper leaf surface paired with a fuzzy, downy growth on the underside, and names it the most serious problem home basil crops face. A second-year gardener who waters overhead in the evening and plants basil in a dense block for a bigger pesto harvest creates exactly the damp, still air the disease needs; by the time the yellowing is noticed, spores have already spread through the planting, and the whole bed of basil is usually lost rather than just the affected leaves.