Sonoma County Master Gardeners Helping Sonoma Gardeners

Nothing at table is quite as evocative of summer as fresh basil—its pungent leaves wafting fragrance up off vine-ripe tomatoes layered with mozzarella, the pungent anise-garlic scent of pesto on fresh pasta, its licorice-like flavor punching up an herb salad dressed with local olive oil and wine vinegar, or in a marriage of strong smells along with chives, coriander, parsley and mint in a fresh salsa verde on a thick steak grilled over vine cuttings.

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.


Sweet Basil (Ocimum basilicum)—large-leafed Mediterranean variety, redolent of licorice and clove—the primary culinary basil, it is much used in Italian cuisine. It grows to a height of 2-2 ½ feet.

Purple or Opal Basil (Ocimum basilicum purpurea)—similar to sweet basil, but with dark bronze-purple leaves. Good for color contrast. Not visually suitable for pesto. A somewhat more tender variety, it grows to about the same height as sweet basil.

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.

Greek or Globe basil (Ocimum basilicum 'Spicy Globe’)—another smaller plant (6-12 in.) which has tiny, compact leaves, and a spicy character—very useful for salads, with soft stems. Compact size makes it a good container plant.

Cinnamon Basil (Ocimum basilicum ‘Cinnamon’)—another spicy variety, with a pronounced cinnamon flavor. It grows to 18-30 in.

Thai Basil (Ocimum basilicum ‘Siam Queen’) - very spicy, with an unusual serrated leaf. Used in Thai and Indian cooking.  Grows to 2-3 feet.

 

 

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.

Culinary Uses

Pesto is a classic way to use and preserve basil. To avoid dulling and to maintain its intense green color, blanch basil quickly in boiling water, dry on towels, and then blend with good extra virgin oil, a pinch of salt, grated fresh Reggiano Parmesan, garlic and pine nuts. Recipes abound—equal proportions of everything except garlic—a third the other amounts—is a good start. Pesto freezes well—it gets grainy, but smoothes on thawing.

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