Basil is easy to grow in warm sunny conditions. It is also easy to grow indoors. Basil is as aromatic in the kitchen as it is in the garden. Cooks around the world turn to basil. It is perhaps most popular in Mediterranean and Asian dishes. It is a great addition to most vegetable, fish, poultry dishes, and summer salads. And, of course, basil is the key ingredient of pesto. Basil is often matched with tomatoes in recipes, and in the garden basil is a companion plant that is said to enhance the growth of both tomatoes and peppers.
Get to Know Basil
- Botanical name and family: Ocimum basilicum, Ocimum crispum, Ocimum minimum
- Origin: India, Central America
- Type of plant: Basil is a tender annual, in subtropical regions, it is a perennial.
- Growing season: Summer
- Growing zones: Zones 4 to 10; basil thrives in warm to hot weather.
- Hardiness: Basil is easily damaged by cold weather and will be killed by frost. Basil can tolerate very warm weather.
- Plant form and size: Basil grows upright in bushy clumps 15 to 30 inches tall and wide depending on the variety. Basil flowers on spikes that grow above the foliage.
- Flowers: Small whitish or lavender flowers grow on spikes at the ends of stems. Pinching stem tips frequently will keep basil from flowering and keep plants bushy and full.
- Bloom time: Mid- to late summer
- Leaves: Leaves are oval, slightly toothed, and pointed, 1 to 2 inches long. Leaves can be bright green or purple-red. Leaves are arranged opposite one another on square stems.
How to Plant Basil
- Best location: Plant basil in full sun, 6 to 8 hours of sun each day. Basil can tolerate light shade. Basil will grow easily in a sunny window.
- Soil preparation: Grow basil in well-drained but moisture-retentive sandy loam. Soil too rich in organic matter or nitrogen will result in lush foliage but low oil content which can affect the strength of flavor and fragrance. Basil will grow in poor soil that is well-drained soil. A raised or mounded bed is a good spot to grow basil. Basil prefers a soil pH of 5.5 to 7.5.
- Seed starting indoors: Start basil indoors as early as 6 weeks before the last frost for planting out to the garden after the weather has warmed—about three or more weeks after the last frost. Basil seed will germinate in about 7 to 10 days at 70°F. Purple leaf varieties need slightly warmer soil temperatures to germinate.
- Transplanting to the garden: Transplant basil outdoors in spring after all danger of frost has passed
- Outdoor planting time: Sow basil directly in the garden or set out transplants no sooner than 2 to 4 weeks after the last frost in spring. A soil temperature of 70°F is optimal for growing basil. Air temperatures in the 80s are ideal. Basil is easily damaged by chilly weather and will be killed by frost. Nighttime temperatures in the 50°sF will cause basil leaves to turn dark or black. Make successive sowings every 2 to 3 weeks to ensure a steady supply through the season.
- Planting depth: Sow basil seed ⅛ to ¼ inch deep; cover seed lightly.
- Spacing: Space plants 12 to 18 inches apart; for small-leafed varieties space plants 6 to 12 inches apart. Space rows 18 to 24 inches apart.
- How much to plant: Grow 4 to 6 plants for everyday kitchen use. Plant 6 to 12 plants if you make a lot of pesto. Grow 8 to 12 plants for preserving. Succession planting will ensure a steady supply of basil.
- Companion planting: Plant basil near tomatoes and peppers to enhance their growth and flavor. The aroma of basil will repel many garden pest insects including flies and mosquitos.
How to Grow Basil
- Watering: Keep the soil just moist; basil prefers moist but not wet soil. Leaves will wilt when basil needs water.
- Feeding: Foliar feed plants with a spray of compost tea or liquid seaweed extract twice during the growing season.
- Mulching: Mulch around basil to suppress weeds and slow soil moisture evaporation in hot weather. Mulch with aged compost or chopped dry leaves. Keep mulch back from stems to avoid stem rot.
- Care: Keep basil pinched back to produce more leaves. Pinch out terminal shoots every two or three weeks. This will encourage branching and more leaves for harvest. Do not prune or cut the woody part of the stem; prune only herbaceous growth. Pinch out flowers as they form; cut back flowering stems by one-fourth; flowering will slow leaf growth. Tall cultivars may need staking. If frost is forecast, harvest the whole plant. Basil will not survive a frost.
- Container growing: Basil is a good container plant. Plant basil in a pot at least 6 inches deep for best root growth. Basil will grow easily in a sunny window.
- Winter growing: Grow basil indoors in winter from summer cuttings or seed. Small-leaved cultivars are a good choice for indoor growing.
- Pests: Snails and slugs may attack basil; handpick them out of the garden and destroy them. Aphids may attack basil leaves; knock them off the plant with a strong blast of water.
- Diseases: Damping-off and fusarium wilt are two fungal diseases that can attack basil. Fusarium wilt and damping-off will cause plants to collapse and die in a day or two. To prevent and control fungal diseases, make sure the soil is well-drained and keep leaves dry. Remove and destroy infected plants. Avoid planting basil in the same spot more than once every four years. Plant fusarium tolerant varieties such as ‘Aroma’.
How to Harvest Basil
- When to harvest: Basil is ready for harvest 50 to 60 days after planting. Pinch out leaves as you need them; regular harvest will keep plants growing strong and prevent flowering When a branch has 6 to 8 leaves, harvest all but the first set of leaves. This will prompt new growth. Harvest leaves in the morning when they are most flavorful. Harvest the entire plant before the first frost.
- How to harvest: Hand-pinch off leaves as you need them; regular harvest will keep plants growing strong and prevent flowering. Avoid bruising or crushing leaves at harvest.
Basil in the Kitchen
- Flavor and aroma: Basil has a subtle peppery flavor. Basil has a fresh licorice-like aroma.
- Leaves: Serve basil with sliced tomatoes dressed with a little oil and lemon juice. Use fresh basil leaves in salads, sauces, pestos, pizza, spaghetti, pasta, rice, cheeses, vegetables, vinegar, soups, stews, lamb, fish, poultry, fruit desserts, ice creams, and bread.
- Cooking: The flavor of basil intensifies when cooked; it’s has a more subtle taste when raw.
Preserving and Storing Basil
- Refrigeration: Fresh basil stores best at 40°F; colder temperatures will turn leaves black. Wash and pat dry fresh basil leaves or dry leaves in a lettuce spinner before refrigerating. Wrap leaves in a damp paper towel and store in the crisper.
- Drying: Basil leaves can be dried. Set leaves on a screen or trays in a well-ventilated spot out of direct sunlight; leaves will dry in 3 to 4 days. Some flavor will be lost.
- Freezing: Quick-freeze leaves to preserve flavor. Place leaves whole or chopped in airtight bags or containers and put them in the freezer. You can freeze basil leaves mixed with olive oil; use 3 cups of packed leaves for ½ cup of olive oil. To preserve basil in vinegar, add 1 cup of packed fresh leaves to 1 quart of vinegar.
- Storing: Store crushed dry leaves in an airtight container.
- Seed: Sow seed in late spring; germination is quick at temperatures greater than 60°F.
- Cuttings: Basil can be started from stem cuttings rooted in water or damp vermiculite.
Basil Varieties to Grow
- Sweet basil (Ocimum basilicum): most commonly grown; 24 inches tall, bright green leaves, 2 to 3 inches long. Sweet basil is most often used for pesto also salads, tomato sauces, and soups. Grow Genovese types including ‘Sweet Basil’, ‘Genoa’, ‘Genovese’, ‘Aroma 1’, ‘Aroma 2’, and ‘Nufar’.
- Lemon basil ( O. b. crispum): good indoor grower; crinkled bright green leaves; more compact than sweet basil.
- Cinnamon basil ( O. b. Cinnamon): also known as Mexican spice basil, has a spicy, fragrant aroma and flavor.
- Greek basil ( O. b. minimum) small leaves, good flavor, add whole leaves to salads and tomato sauces; a good choice for growing indoors
- Holy basil ( O. b. sanctum) use in Thai cooking, stir-fried with chicken, beef, or pork
- Purple basil ( O. b. ‘Dark Opal'): reddish-purple leaves used often in Asian cooking. Other purple varieties include ‘Purple Ruffles’, ‘Red Lettuce Leaved’, ‘Red Osmin’, ‘Red Rubin’, ‘Rubra’.
- Thai basil (O. b. var. thyrsiflora) has a sweet licorice flavor.
- Miniature basil ( b. ‘Minimum')” short, compact sweet basil; a good choice for growing indoors.
- Tree basil (O. b. gratissimum): grows to 6 feet tall; use as other basils.
- Camphor basil (O. b. kilimandscharicum): strong camphor fragrance.
- Thai basil (O. basilicum ‘Horapha’; used in Thai cooking.
- Tulsi or sacred basil ( O. b. sanctum): strong clove aroma; use fresh not for cooking.
- Large leaf varieties: ‘Napolitano’, ‘Large Green’, ‘Mammoth Sweet’.
- Compact varieties: ‘Finissimo Verde a Palla’, ‘Greek’, ‘Spicy Globe’, ‘Magical Michael’, and ‘Marseillais Dwarf’.
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