Written by Brittnay Haag at the University of Illinois Extension Center

Nothing says summer like enjoying the freshly harvested vegetables and herbs from your garden. “One of the easiest, most prolific, and flavorful herbs to grow is basil (Ocimum basilicum),” states Brittnay Haag, University of Illinois Extension Horticulture Educator. While there are many cultivars of basil, the most common are sweet basil and Genovese basil.

Basil grows best in sunny locations (6 to 8 hours of sun each day), and well-drained, fertile soil. It can also grow well in containers or raised beds that have adequate drainage. Basil is cold sensitive so it must be planted outdoors after the chance of frost has passed. When planting basil, proper spacing is crucial to provide good air circulation between the plants and decrease the likelihood of disease. Space plants at least 2 feet apart. Basil can also be directly seeded in the garden after the threat of spring frost has passed.

Apply two to three inches of mulch around the base of basil to retain water moisture and reduce weeds around the plant. Water plants regularly to guarantee good growth and development. When watering basil, water at the base of the plant or use drip-irrigation, or drip hoses to ensure the foliage stays dry. Depending on rainfall and temperatures, plan to water basil at least once a week, and more often when temperatures are hot. Plants grown in containers will dry out faster than in-ground. Plants that are overwatered or underwatered may develop weak, spindly growth or roots may rot.

If plant growth is reduced and the foliage has become a paler green color, basil can be cut back fertilized every three to four weeks with a liquid fertilizer, following directions on the manufacturer label. Over-fertilizing herbs can result in decreased aroma and taste, so don’t overdo it.

An important task when growing basil for culinary uses is to keep the plant from blooming. If it flowers and develops seeds, the plant will become woody, stop producing and the foliage will become bitter tasting. Continue to remove blooms all season.

If grown for the ornamental value and you don’t intend to harvest the foliage, there is no need to cut the blooms off of the plant. Some varieties even have showy blooms, including some of the purple-leafed varieties with small pink blooms on a spike. 

When harvesting the foliage, cut the whole stem just above a pair of leaves, leaving at least half of the plants. New growth will appear at the cut point within a week. Individual leaves can also be harvested. Freshly harvested basil stores best (and for a couple of days) in a vase of water at room temperature.

During the peak of the season, you may have more basil than you know what do with! Basil leaves can be dried on the stem- hang the foliage upside down in small bundles in a warm, well-ventilated room for one week. Dried leaves can be stripped from the stem once dried and either stored in an air-tight container either whole or ground up. For a fresher flavored product, basil leaves can also be frozen- whole leaves in plastics bags or chopped into small pieces in an ice-cube tray and a little water.

While pests and diseases are not always a problem when growing basil, some common issues to watch out for are gray mold, leaf spots, and Japanese beetles. Gray mold and leaf spot occurrences can be reduced by watering at the base of the plant and avoiding wet foliage, especially during harvest. Japanese beetles can skeletonize the foliage for 4-6 weeks during the summer. They should be hand-picked from the plants and dropped in a bucket of soapy water. Plants can also be covered with a light-weight row cover to protect the foliage from the beetles.

“Basil is a tender annual and will not survive Illinois winters outside, but dig up your basil plants before the first freeze and bring them inside to extend their growing season by a couple of months,” recommends Haag. Supplemental lighting may be necessary to keep the plant growing.