Although commonly found in delicious, Italian dishes, basil is thought to have originated in the Far East and was first cultivated in India. While this plant doesn’t care for cooler weather, it’ll grow in abundance in most areas once frosts have passed. Basil also makes a great container plant that can be moved indoors when cold weather approaches. Basil comes in many colors and sizes, with most common varieties growing 1–3′ tall with green or purple glossy leaves and red, purple, or white flowers.
Dark Purple Opal basil is a colorful cultivar that grows purple serrated leaves with an occasional splash of green thrown in for fun. Leaves tend to be darker on older plants. The taste is described as milder than the green basil types. This basil is a good choice for use as a garnish or to make a basil-infused vinegar with a nifty purple hue. Plants will reach 12–18″ in height and are favored because they are slow to bolt. When it does bolt, expect a spray of cute purple flowers, making it a great decorative plant.
Seed Depth: 1/8–1/4″
Space Between Plants: 4–8″
Space Between Rows: 12–18″
Germination Soil Temperature: 65–85°F, optimum 70°F.
Days for Germination: 5–10
Sow Indoors: 6–8 weeks before average last frost date.
Sow Outdoors: 1–2 weeks after average last frost date.
Vegetative: Can be started from stem cuttings. Root in a jar of water or sterile soilless mix.
Basil is a semi-tropical herb and likes sunny days and comfortable temperatures. Because its leaves are slightly succulent, basil doesn’t tolerate temperatures below freezing. Mild zones, like those above USDA Zone 5, exhibit ideal climate conditions for growing basil as an annual. This cultivar is grown as a perennial in Zones 9–11.
Natural: 4–6 hours of full sun. Tolerates partial sun. Basil will do just fine on a sunny windowsill.
Artificial: Will grow well under artificial lamps such as a compact fluorescent with 8–12 hours of light per day.
Soil: Prefers a well-drained loamy soil. A pH of between 6.0 and 7.0 will keep plants healthy and nourished.
Soilless:Start seeds in a soilless mix or mineral wool cubes. Container-grown plants will do well with a soilless mix with added nutrients.
Hydroponics: Thrives in a variety of hydroponic systems, including NFT or a media-based hydroponic system. Use clay beads, perlite, coco coir, a soilless mix, or a combination.
Aeroponics: Cuttings will root easily in an aeroponic system.
Water: Requires moderate levels of water. Consistently moist soil is best, but take care not to overwater. Use drip irrigation or carefully hand water to avoid getting leaves wet.
Nutrients: Requires moderate to high levels of nutrients. Amend soil with compost before planting or transplanting. Feed plants every 2–3 weeks during the warm growing season.
Foliar: Will benefit from a foliar spray of diluted Epsom salts if the soil is deficient in magnesium.
Pruning: When seedlings have 3 sets of true leaves (not counting the initial seed leaves), pinch off the top set. Continue this pattern when harvesting, pruning each branch you harvest back to just above its first or second set of leaves. Keep pinching off flowers as your basil grows to extend its harvest time. Flowering will change the flavor of leaves and reduce leaf production. Like many herbs, basil does well with relatively heavy and frequent harvests or pruning.
Mulching: Use mulch to suppress weeds and conserve soil moisture.
Deficiency(s): A nitrogen deficiency can become a problem with the basil plant, indicated by stunted growth and discoloration of the leaves. Liquid seaweed or compost tea will amend this issue.
Rotation: Rotate plots of basil every year.
Companions: Plant near tomatoes, peppers, oregano, and petunias. Avoid planting near sage or rue.
Harvest: Start harvesting as soon as your basil reaches maturity, about a month or two after planting. If using fresh, harvest your basil as needed, just before use. If you want to dry your basil and take an entire harvest before flowering or frost, cut sprigs to the soil level and hang upside down for drying in a warm, dark, well-ventilated area.
Storage: Fresh leaves will not keep over two or three days, even with refrigeration. Crumble dried leaves into an airtight container to keep for over a year.
Fun Fact: This basil variety was first developed in the 1950s at the University of Connecticut by John Scarchuk and Joseph Lent. It won the All American Selection Award in 1962.
Preserve: Making a pesto out of fresh basil leaves will help preserve that summer taste a bit longer. Simply grind up the basil with oil, garlic, your choice of nuts, and cheese (optional) in a food processor. You can store your homemade pesto in the refrigerator for about a month or freeze for up to three months. Another option is drying basil leaves for use as a dried herb. Cut stems and hang upside down for drying in a warm, dark, well-ventilated area. Ground or finely chopped leaves can also be frozen in ice cubes with water or oil.
Prepare: Fresh basil can be added to any dish. Pesto makes a great garnish to pastas or as a spread on just about anything.
Nutritional: Provides vitamin(s) K, C, beta-carotene (which is converted into vitamin A), calcium, potassium, magnesium, and iron.
Medicinal: Basil has anti-inflammatory properties. It is also used as a digestive aid and to reduce gas, nausea, and stomach cramps. Seed extracts and oil have antibacterial and antiviral properties. Topical applications of basil leaves may help to reduce itching associated with insect bites. The scent is used in aromatherapy to support mental healthy and invigoration. It’s prominently used in the ancient Ayurvedic system of India as well.
Try out this tasty Purple Pesto Soup with your purple basil leaves.