Sweet Basil, Ocimum basilicum, is the most widely grown for kitchen purposes. It's history goes back thousands of years to the "Old World". It has been cultivated thought the Mediterranean especially Africa for centuries, where it is native. Basil is one of the most popular fresh herbs grown for chefs and home cooks as well. It is a tropical plant that must be planted after any danger of frost. Once the overnight temperatures stay above 60° F and daytime temperatures are 80° or above, Basil will grow explosively.
Plants started ahead of time or transplants will give at least a six week head start to the season over direct seeding in the ground. Make sure the soil is of medium fertility around 6.4 pH and a good mix of sandy loam will provide best results. Basil cannot tolerate any water stress, so water regularly or use drip irrigation to make sure the root system can permeate the soil and develop well. Over watering can cause root rot or soft rot where the plant develops a dark area in the stem and stops growing. Plant at least 12 to 18 inches apart as the plants will get quite bushy and good air circulation is needed too. Trim back or prune the main stem weekly to discourage flowering and encourage branching and higher yield of leaves. Once Basil flowers, all energy go to the flowers and making of seed. Thus, leaf production will end and leaves will begin to turn yellow starting at the bottom of the plant.
Harvest when the plant is about 12 inches tall, making sure the plant is more than 6 inches tall after each harvest, or regrowth will not occur. If growing more than one plant, harvest plants alternately, ensuring plenty of yield at each harvest time.