Watering : Ensure that your basil plants receive approximately 1 1/2 inches of water per week.
Soil : Basically any fertile soil will grow Basil.
Harvesting basil is important, not only to promote the growth of new stems but to ensure that the plant does not flower too early. Once the herb starts to flower it will stop producing new leaves and the existing leaves may become slightly bitter to taste. If you are growing basil outdoors make sure to harvest all the leaves before the first frost, or transplant it indoors so that your crop is not lost.
Plant near : Most garden crops, Basil improves the flavor and growth of garden crops (especially tomato and lettuce), it repels flies and mosquitoes.
Keep away from : Rue
Diseases : Fusarium wilt will quickly kill younger basil plants. Seedlings may also be killed by Pythium damping off, gray mold can cause infections post-harvest and is capable of killing the entire plant, Black spot can also be seen on basil foliage,
Basils varieties commonly sold in the USA : African blue basil, Anise basil, Camphor basil, Cinnamon basil, Dark opal basil, Globe basil, Hoary basil, Holy Basil , Spice Basil, Lemon basil, Lettuce leaf basil, Purple basil, Queen of Siam basil, Rubin basil.