Do not purchase transplants that show brown streaking on the stem. This is likely fusarium fungal disease, which causes sudden wilting of the leaves and the eventual death of the plant. It can also contaminate the soil for years. Fusarium has been a serious problem for the basil industry. Basil can be planted now.
Basil loves heat.
It is very sensitive to cool temperatures, and will be devastated by any hint of frost. Basil prefers a fertile, well-aerated, organically rich soil. Basil appreciates regular fertilization and watering. Basil should be cut for use before the first flower buds open, and harvest may begin as soon as the young plants begin to stretch up. The tips can be pinched out to encourage branching, and the tips can be used for cooking.