Growing Basil
Basil (Ocimum basilicum) is the single most popular culinary herb grown in home gardens, and for good reason. It is fast-growing, highly aromatic, and used across dozens of cuisines worldwide. Sweet basil is the classic variety found in Italian cooking, but Thai basil, holy basil, lemon basil, and purple basil each bring their own character to the garden and the kitchen.
Varieties Worth Growing
Sweet Basil (Genovese) is the standard for pesto, Caprese salad, and Italian sauces. It produces large, tender leaves with a sweet, slightly peppery flavor. Thai Basil has smaller leaves with a distinct anise-licorice flavor and holds up better to heat in stir-fries and curries. Purple Basil (such as 'Dark Opal') adds a striking visual element to the garden and a milder flavor. Lemon Basil is wonderful in seafood dishes and teas. For adventurous growers, Holy Basil (Ocimum tenuiflorum) is the basil used in Thai pad kra pao and has a spicier, more clove-like taste.
Planting
Basil is a warm-season annual that cannot tolerate frost. Direct-sow seeds outdoors after all danger of frost has passed and soil temperatures are consistently above 60°F (16°C). Alternatively, start seeds indoors 6–8 weeks before the last frost date. See Seed Starting Herbs Indoors for detailed instructions.
Plant seeds about 1/4 inch deep in moist, well-draining soil. Thin seedlings to 8–12 inches apart once they have two sets of true leaves. Basil does well in garden beds, raised beds, and containers — a 10-inch pot can support one or two productive plants.
Sun, Soil, and Water
Basil needs full sun — 6 to 8 hours minimum. It prefers rich, well-drained soil with a neutral to slightly acidic pH (6.0–7.0). Amend heavy or clay soil with compost. Water regularly, keeping the soil evenly moist but not waterlogged. Basil wilts dramatically when thirsty but recovers quickly after a good drink. Mulch around plants to retain moisture and suppress weeds — old straw bale material makes good mulch for this purpose.
Pinching and Harvesting
This is the single most important thing to understand about basil: pinch early and often. Once a plant has 3 sets of leaves, pinch off the top set just above the node. This forces the plant to branch, giving you a bushy plant with many more leaves rather than a single tall stem. Continue pinching growing tips every week or two throughout the season. Always pinch off flower buds as soon as they appear — once basil flowers, the leaves turn bitter and the plant puts all its energy into seed production.
Common Problems
- Bolting: Basil bolts (flowers and goes to seed) in hot weather, especially in mid-to-late summer. Regular harvesting delays bolting. Some varieties like 'Everleaf' are bred for slower bolt times.
- Downy mildew: A devastating basil disease that causes yellowing leaves and gray-purple fuzz on undersides. Improve air circulation, avoid overhead watering, and look for resistant varieties like 'Amazel' or 'Devotion'. See University of Minnesota Extension for more on this disease.
- Aphids and Japanese beetles: Hand-pick beetles; spray aphids off with water or treat with insecticidal soap.
- Cold damage: Basil blackens at the slightest frost. Cover plants or bring containers indoors if an unexpected cold snap is forecast.
Using Fresh Basil
Fresh basil is best added at the end of cooking to preserve its aroma. It is indispensable in classic pesto, Caprese salad, Thai curries, Vietnamese pho, and countless pasta sauces. Tear leaves rather than cutting to avoid bruising. Basil does not dry as well as some other herbs — much of the flavor is lost — so use it fresh whenever possible, or preserve it by freezing in olive oil.