By: Deborah Wechsler
Basil likes a fertile soil, though it tolerates a wide range of pH (4.5 to 6.5). Although some folks insist that the flavor is better if basil isn't fertilized, grows and looks better if it's fed at planting time, and again during the season, perhaps after a heavy picking. Supplemental irrigation can double yields, Simon reports.
Like most herbs, basil has few pests. Japanese beetles can easily be kept off with spunbonded polyester row covers. If slugs are a problem on new transplants, try using a barrier of copper flashing.
A devestating disease, fusarium wilt of basil, reached North America via infected seed in the 1990s. Symptoms include sudden wilting and leaf drop, accompanied by dark streaks on the stems, usually in weather above 80°F. If you notice the symptoms, quickly dig up the infected plant, along with all soil around the roots, and discard it. If part of your garden becomes infected, avoid spreading the disease by moving soil around on your tools or tiller, and consider growing your basil in containers. You can also try your luck with a fusarium-resistant variety, such as 'Nufar'.
Basil is also susceptible to a few bacterial rots that show up on stems or leaf clusters, usually in cool, wet weather, in winter greenhouse production, or late in the season. Planting in well-drained soil, spacing plants so they dry out after they're watered, and practicing good garden sanitation are the keys to control.