Background and Varieties
Basil is a kingpin of the kitchen garden, with great bushes of it perfuming the summer afternoon air, and takes well to pots in a sunny window or on the deck. While normally thought of as Italian or Mediterranean, basil originated in Asia—the Indian sub-continent, Thailand, Vietnam. There are many types of basil, ranging from the usual large leafed Mediterranean sweet basil, to the globe-shaped tiny-leafed Greek, purple, spicy Thai, citrus-y lemon and lime basil, and even chocolate. All of these variations in aroma stem from slightly different levels of essential oils in the different plant varieties.
Lemon or Lime Basil (Ocimum basilicum citriodorum)—a smaller plant (12 in.) with a mild citrus aroma and flavor. It is often paired with grilled fish.
Cultivation and Care
Basil is quite sensitive to cold, and is best grown with good hot summer sun. Lots of hot sun is the key to success. A few types of perennial basil exist, but all types for culinary use are annuals. Basil can be sown from seed indoors, or in a hothouse, and then planted out in spring – generally May in Sonoma County. You can still find plants in the nurseries now, though, and it will grow quickly with the hot, long, days of summer. Plant-to-harvest is about 10 weeks. It is easy to root basil cuttings in a glass of water, and then transplant. Plant in well-drained soil in full sun. Frequent harvesting of the outer leaves will prolong the life of the plant. Once basil flowers, leaf production slows, and essential oil production declines. Unless you are looking for seeds, or a few flowers for decoration, pinch off any flower stems before they mature.
Basil has a reputation as an insect repellent, particularly for mosquitoes, although there is little actual data to support this! Despite its insect repellent reputation, basil is subject to a variety of pests, including whiteflies, slugs, aphids, spider mites, Japanese beetles, cutworms and nematodes. Many adult insects can be avoided by covering plants with fabric row covers during the day.
Whiteflies can be controlled as usual with a strong stream of water to remove the flies. Or a natural insecticidal soap can be used. Slugs should be controlled with Sluggo.
Cutworms can kill plants in the period after transplanting. To prevent infestation, add wood ashes to soil or place a cutworm collar around the base of the plant.
Mealybug control is not simple: thwart the ants that carry the mealybugs on to the plants with diatomaceous earth, spray with natural Safer's soap; swab mealybug egg masses with alcohol.
While not frequent, basil can suffer from several plant pathogens, including fusarium wilt, black spot caused by the fungi genus Colletotrichum, and gray mold caused by Botrytis cinerea.
Another way of preserving basil for later use is to layer the leaves in a jar, with light dustings of fine sea-salt. Fill the jar with good olive oil, seal the lid tightly and place in a cool, dark spot. Use the leaves as needed and reseal each time. This will keep for several months (light is an enemy). To make basil oil, tightly pack a jar with leaves, crush slightly with a pestle to release oils, and fill with good olive oil. The oil will become infused with the essence of basil in a month or three. Bottle it and use it sparingly in dressings, on fresh grilled fish or in pastas. Chop Thai basil with mint, garlic, ginger and Thai chilies and freeze in small cubes to add to stir-frys or vegetable dishes.
So plant it widely, in multiple varieties, and use it generously throughout the summer and early fall, and then enjoy the preserved concoctions throughout the winter.
©Sonoma County Master Gardeners