Basil grows between 30–130cm (12–51 in) tall, with opposite, light green, silky leaves 3–11cm (1.2–4.3 in) long and 1–6cm (0.39–2.36 in) broad. The flowers are small, white in color and arranged in a terminal spike. Unusual among Lamiaceae, the four stamens and thepistil are not pushed under the upper lip of the corolla, but lie over the inferior lip. After entomophilous pollination, the corolla falls off and four round achenes develop inside the bilabiate calyx.

Basil is very sensitive to cold, with best growth in hot, dry conditions. It behaves as an annual if there is any chance of a frost. In Northern Europe, Canada, the northern states of the U.S., and the South Island of New Zealand it will grow best if sown under glass in apeat pot, then planted out in late spring/early summer (when there is little chance of a frost).Additionally, it may be sown in soil once chance of frost is past. It fares best in a well-drained sunny spot.