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This service operates out of The LuEsther T. Mertz Library where the staff relies heavily on the Library’s collections and uses their field knowledge and experience to research and formulate their answers. Questions about outdoor and indoor plant culture, selection, identification, sourcing and maintenance are addressed. The service provides valuable information on cultural requirements such as planting, fertilizing, pruning and propagation as well as assistance with landscape design inquiries.
Basil: Knowing and Growing
The botanical name for basil is Ocimum basilicum. The genus Ocimum comes from the Greek word Okimon, meaning smell, and the species, basilicum, is the Latin translation of the Greek word basilicon, meaning kingly herb.
Basil is an aromatic herb used fresh or dried. It has been used for more than 2,000 years throughout many lands and is native to Africa, Asia, the Middle East, the Caribbean and South America. Ocimum, of the mint family Lamiaceae, is identified by its square stems and opposite leaves. Some of the plants in this family include the herbs thyme, oregano, rosemary, lavender and mint. Today, cultivated "sweet basil" is used to enhance the flavor of many foods and beverages. The taste and scent of basil can be of mint, cinnamon, anise, vanilla and clove. Floral notes of basil vary from hyacinth to citrus.
Sweet basil is identified by leaf edges that cup slightly and form a pointed end. The leaves are glossy, long and almond-shaped. Basil has many compounds, but three, linalool, methyl chavicol and eugenol, stand out as primary contributors to its signature aromas. Linalool is a significant part of the aroma of lavender plants. Methyl chavicol gives some sweet basils a hint of anise flavor and eugenol gives a clove-like aroma.
Early explorers found that basil was considered sacred and possessed supposed supernatural powers. Holy basil (O. sanctum) is one such herb used in the Hindu religion. The Spanish, French, Portuguese and English colonists brought basil to the New World. It was brought to the Massachusetts Bay Colony in about 1621. There are 35 basil species and cultivated varieties are numerous.
Ocimum basilicum 'Genovese Verde Migliorato' or 'Genovese' is reproduced from seed. Genoa basil is a favorite for pesto in America and Italy. Germination takes 3 days at 70°F; transplant 12 days after sowing; it is ready to transplant to the garden 26 days after sowing. First flowers appear 56 days after sowing and the plant will be approximately 26" high x 14" wide.
Ocimum americanum 'Genoa Profumatissima' is a popular basil in Italian cuisine. It is similar in appearance to Genoa basil but has some flavor variation. Germinate its seed as you would for 'Genovese'. The aroma has a balance of licorice, citrus zest, cinnamon, spice and mint.
Ocimum basilicum minimum, bush basil, is bushy and upright with tiny aromatic leaves. It grows well in containers and makes some of the best pesto, so is popular with chefs.
Tips When Using Basil Fresh or Dried
When cooking with dried basil, crush it with your fingers or in the palm of your hand. Crush fresh basil leaves carefully with coarse kitchen salt and a whole clove of garlic as an option. If dried leaves lose their flavor, restore them by warming again in the oven on a cookie sheet set at the lowest temperature for a few minutes or until fragrant.
Scented basils (Ocimum basilicum odoratum) include lemon basil, cinnamon basil and licorice or anise basil. Try cinnamon basil with jellies, custards, fruit salads or meat marinades. Anise basil imparts a sweet fennel-like flavor to Asian or Italian cuisine and adds good flavor to poached pears and melon. Lemon-flavored basil adds a mild citrus flavor to stir-fry vegetables. Scented basil varieties can be used for sachets or dried wreath arrangements.
Growing Basil in the Garden
Basil is easy to grow and treat as an annual in the home garden. Basil likes full sun and well-drained soil that is not overly rich. Sow seeds indoors five or six weeks before the last frost. Seeds will germinate at a temperature of 65 to 75°F in a few days. Transplant outdoors when the weather is consistently warm, above 65°F. Seedlings should have 3 pairs of leaves when transplanted. Space plants about a foot apart in the garden bed. If direct seeding into the garden outdoors, thin seedlings to one foot apart. When flowers appear, cut plants back to 6 inches to stimulate more growth. Nipping flowers just stimulates growth of more flowers in the axils of the leaves. To regenerate vegetative growth, basil stems must be cut back hard.
- Light: 6 hours of sun a day (best grown in bright, sunny summer conditions)
- Temperature: night temperature should be above 60°F outdoors
- Soil pH: 4 to 7.0
- Water: water well, about an inch a week during morning hours. Keep cold water off the leaves to deter black spot disease.
- Harvesting: basil can yield an ongoing supply of leaves if picked often, but cut and use right away for best taste.Cut, do not pull, enough of the stem to leave only two to four leaves on the plant. Plants will reproduce two to four new branches for harvesting.
- Propagation: can be done by seed or cuttings. Basil is one of the most prolific herbs. A single flower stem contains about 120 to 240 seeds or nutlets. Basils are self-fertile, and cross-pollinate easily if more than one variety is grown in the same vicinity.
Growing Basil in Pots
Basil is prone to root rot caused by soggy soil in too large a pot. When selecting potting soil, use fresh soilless potting mixtures available from the nursery. These mixtures are spongy, soft and well drained, just what a fast-growing plant like basil prefers. When watering, check soil moisture with a finger test. If it is moist don't water yet; if the mix has lightened in color, it's time to water. You can also tell by the weight of the container. If it is dry, the pot will be lighter than when thoroughly watered with wet, heavy soil. Basil can be grown indoors on a windowsill that receives at least 6 hours of direct sun a day.
Place cut stems in water on the windowsill, not in the refrigerator, which is too cold for basil's tender leaves. To dry basil, harvest leaves from outdoor plants in the early morning after the dew is gone; do not wash the leaves before drying. Brush off any soil remaining and tie together bunches of 3 to 5 stems each. Hang bunches upside down in a dark, airy, warm area for 2 to 4 weeks.
To dry basil in a few days, place leaves on a cookie sheet pan in the oven and set at the lowest temperature. Once dried, crumble and spread basil leaves on newspaper, pour into sealed jars and store in a cool dark place.
Whole basil leaves can also be kept in the freezer where the leaves will turn black but the flavor will be preserved. Just wash leaves with water and dry them in a colander or salad spinner. Place between paper or cloth towels to absorb any moisture. Pack the leaves in plastic bags, seal and freeze.
The best way to preserve basil and keep its green color is to keep it in olive oil. Use a sterilized jar and layer whole or chopped leaves until they are one inch from the top of the jar. Pour in the olive oil to cover the leaves and cap tightly. Store in the refrigerator and use basil-flavored olive oil for pasta, vegetables or salad.