University of Illinois Extension

Basil in the Garden

Basil, Ocimum basilicum, is one of the most popular herbs grown today, an easy-to-grow annual that can be planted in the ground or in a container, said a University of Illinois Extension horticulture educator, Susan Grupp.

“Whenever I visit an herb garden, I know I will find basil,” said Grupp. “It is an important culinary herb, grown primarily for its fragrant leaves. Its warm, rich, and spicy flavor is popular in Italian, Mediterranean, and Thai cooking.”

Basil requires full sun and warm temperatures. It should be placed in a location that is protected from strong wind.

“You can start seeds indoors,” she said. “Buy small transplants from a garden center or direct seed into the garden. It is very important to wait until all danger of frost and even cold temperatures have passed. Basil loves warm temperatures, and can be injured if the temperature drops below 50 degrees F. Also, be careful when watering young seedlings. If over-watered, they may develop a fungal disease called damping-off.”

After the plants have developed a few pairs of leaves, they should be thinned so plants are eight to 12 inches apart. There are many basil species and cultivars, she noted. Some are dwarf and compact and grow only eight inches tall compared to others which might grow 18-24 inches tall.

“By mid-summer, basil produces small, white, or pinkish-white flowers,” Grupp said. “If you are growing basil for culinary uses, then you should remove the flowers and also prune the plant every few weeks. This will encourage new succulent growth and provide a steady supply of young leaves.

“Some basils, with their beautiful foliage and attractive flowers, may be left alone and enjoyed for their ornamental sake. If you leave the flowers and don’t prune, the plant tends to get woody and you’ll have fewer succulent leaves to snip.

To harvest basil, simply cut the stem back so one or two pairs of leaves remain. Basil should recover quickly in warm weather.

“Basil can be used fresh or dried,” she said. “Add chopped or minced fresh basil to recipes or toss whole leaves in a salad. To dry the leaves, hang small bunches of stems with leaves attached, or lay them flat on a drying rack, and allow to air dry in a warm, dry room. In about one or two weeks, remove the leaves and store in an air-tight container. Keep out of bright light and away from heat.”

You can continue to harvest basil until the first frost. Since it is a tender annual, be sure to harvest a lot before winter arrives.

“With so many variations of leaf shape, texture, and growth habit, you could consider planting several basils in your garden,” said Grupp. “In addition to the standard type, Sweet Basil (O. basilicum), there are several other varieties that should do well in Illinois.”

Grupp finds that Spicy Globe (O. basilicum ‘Spicy Globe’) with its compact and bushy growth works well as a border plant in herb gardens and looks great in containers. It has much smaller leaves than Sweet Basil and they are strongly flavored. Dark Opal Basil (O. basilicum ‘Purpurascens’), with its dark purple foliage, provides a nice contrast in the flower garden with other flowers. Other worthy basils include Green Ruffles Basil (O. basilicum ‘Green Ruffle’) with its lime green, serrated, and ruffled foliage, Purple Ruffles Basil (O. basilicum ‘Purple Ruffles’) with its dark, maroon ruffled leaves, Cinnamon Basil (O. basilicum ‘Cinnamon’) an interesting selection with nice cinnamon fragrance and flavor, and Lemon Basil (O. basilicum ‘Citriodum’), a fine-textured plant with a lemon scent.