How to Grow Basil: Planting, Pinching, and Harvest

Basil (Ocimum basilicum) is a warm-season annual herb that requires more heat than most other common culinary herbs. Get the temperature and light right, pinch it correctly, and basil is one of the most productive herbs for a home garden or windowsill.

Temperature and Planting Time

Basil does not tolerate cold. It is damaged at temperatures below 10 degrees Celsius and killed by frost. Do not transplant outdoors until nighttime temperatures are reliably above 15 degrees Celsius and all frost risk has passed. In most of the northern United States, this means planting in late May to early June.

For a head start, sow seeds indoors 4 to 6 weeks before the last frost date. Basil seeds germinate best at soil temperatures above 21 degrees Celsius, so a heat mat under the seed tray significantly improves germination rate in cooler indoor environments.

Soil, Sun, and Planting

Basil grows best in fertile, well-draining soil with a pH of 6.0 to 7.0, and needs full sun of at least 6 hours per day to produce the essential oil content that delivers full flavor. Plants in partial shade grow but have less intense flavor. Space transplants 20 to 25 centimeters apart. Basil grows well as a companion to tomatoes, sharing their preference for warm, sunny conditions.

Pinching: The Key to Productive Basil

Pinching is the single most important management technique for basil. Left unpinched, basil quickly grows tall, flowers, sets seed, and declines in leaf quality. Pinch by removing the growing tip at the top of each stem, cutting just above the uppermost pair of leaves. Two new stems will grow from the nodes below the cut, doubling the number of productive stems. Repeat every two to three weeks through the growing season. Begin pinching once the plant has produced five to six pairs of leaves.

Remove any flower buds immediately when they appear. Once a basil plant begins flowering, leaf quality declines rapidly.

Harvesting

Harvest basil in the morning when essential oil content is highest. Cut or pinch stems back to just above a pair of leaves, never stripping individual leaves. Regular harvesting serves as pinching simultaneously and keeps the plant in vigorous production all season.