Conduct a soil pH test on the area where you intend to grow basil at least three months prior to planting. Basil needs a soil pH range between 6.0 and 7.5 in order to absorb the soil's nutrients, and it takes three months to alter the pH range with soil amendments. Dig a 6-inch hole and collect soil from the bottom of the hole. Follow the directions provided with the test. Amend acidic soil---soil with a pH under 6.0---with lime. Spread sulfur over alkaline soil, which is indicated by a pH over 7.5.
Broadcast basil seeds over the planting area. Cover the seeds with 1/4 inch of soil. Water the area, so that the soil is moist.
Remove seedlings when they develop two to three leaves. Dig up the seedlings and space them 6 to 12 inches apart. Water the soil at least every seven days or as needed to keep it moist.
Spread a layer of 2 to 3 inches of mulch around seedlings to retain soil moisture and prevent weeds from interfering with your plants.
Apply a 5-10-5 fertilizer---no more than twice during the growing season---at a rate of 3 oz. for each 10 feet of row.
Harvest whole stems by cutting underneath pairs of leaves with bypass shears. New growth will emerge from the cutting point in a week. Harvest leaves as needed by gently grasping them between thumb and index finger and snapping them off the plant.