Basil, Ocimum basilicum, is a member of the mint family and a popular annual herb. It is native to Asia (India, Pakistan, Iran, Thailand, and other countries). Because of its popularity, basil is often referred to as the "king of the herbs".
Basil plants can grow up to two feet in height. Both leaves and stems are used fresh and dry. Leaves are normally green, but several cultivars have burgundy or purple leaves. Flowers range from white to shades of pink and purple, and appear from late July into August. In temperate regions like Iowa, plants are typically grown from seed each year. However, plants can also be propagated by cuttings and can successfully be grown indoors on a sunny windowsill.
Growing | Harvesting | Drying & Freezing | Potential Problems | Basil Downy Mildew | Types | Uses | History | More Information
Growing
Basil is a tender perennial grown as an annual. It can be grown easily from seed. Start seeds indoors 4 or 5 weeks before the last frost date. It likes warm temperatures (about 75°F) for germination. Keep seedlings in bright light to prevent lanky plants that do not transplant well. Plant basil outdoors after all danger of frost is past. Basil does not tolerate cold temperatures and is readily damaged by frost. Seed can also be sown directly in the ground outdoors in spring after night temperatures are consistently above 50°F. Plants can benefit from pinching in mid-spring to promote branching. While they may not grow much in cool spring weather, plants grow rapidly during the warm weather of summer.
Plant in full sun with moist, well-drained soils and avoid heavy nitrogen fertilization. Too much nitrogen affects its flavor. While established basil is relatively drought-tolerant, regular watering in dry weather promotes plant growth.
Basil is well-suited for growing in containers. It can also be grown indoors in a sunny window. Plants grown indoors will have a less intense flavor and fragrance.
Harvesting
For maximum flavor, basil should be harvested when flower buds have started to form but before they begin to open. Much of the flavor in the leaves will have dissipated once the seed has formed. If stem tips are removed, plants will branch and form more growth that can be harvested once it is large enough. This can allow for an ongoing harvest much of the summer into fall.
After cutting, wash and pat leaves dry. Use immediately or store in perforated plastic bags in the refrigerator.
Drying & Freezing
Drying basil on racks or trays is the preferred method, rather than tying it in bunches and hanging it. To protect the leaves from dust, the trays or racks can be covered with a sheet of cheesecloth. They should then be placed in a warm, well-ventilated area, away from direct sunlight.
Once fully dried, basil should be brittle to the touch while still retaining its original green or purple color. If the leaves turn brown, it indicates they were exposed to excessive heat during drying, which results in a significant loss of flavor.
Once basil leaves are fully dried, they should be transferred to airtight jars immediately to prevent contact with moisture, which can cause rehydration and a musty odor. Small, dark jars are ideal and should be sealed tightly. If using clear jars, they must be stored in a dark place to avoid fading and loss of flavor due to light exposure. Alternatively, dried basil can be stored in small, tightly sealed plastic bags or any closed container that keeps out air and light.
Basil can also be preserved by freezing. Leaves can be placed in freezer bags. Basil "ice cubes" are great for sauces and soups. Chop the leaves and mix with some water. Put in ice cube trays to freeze and store the cubes in freezer bags.
Potential Problems
Overall, basil has few problems. Occasionally, slugs and snails can eat holes in leaves, especially in plantings with too much shade or that are overly wet or crowded. Thrips may cause some leaf discoloration on occasion. Fusarium wilt can also be problematic in settings where the pathogen is prevalent.
Basil Downy Mildew
One serious disease issue can cause significant loses for basil, basil downy mildew. The first noticeable symptoms are yellowing between the veins, possibly imitating a nutritional deficiency. If you flip over the yellowed leaves, you may see gray fuzzy growth on the underside of the leaf. The leaves will then blacken and die.
Downy mildew is caused by a fungus-like organism called Plamospora belbahrii. This pathogen thrives under warm, wet weather conditions. Downy mildew is spread through infected seed, transplants, or fresh leaves. Once in your garden, downy mildew can spread through rain splash, overhead irrigation, and wind. It also produces a type of spore (called an oospore) that can remain inside infected plant material for several years.
If you suspect downy mildew on your basil or find fuzzy growth on leaf undersides, bag and remove the plants immediately. A few resistant varieties are available, and those are the varieties that should be planted in your garden moving forward. To reduce the risk of infection, avoid overcrowding and promote air circulation among plants. Also, avoid overhead irrigation and watering at night.
Resistant Varieties
The popular cultivar 'Genovese' is one of the most susceptible varieties to basil downy mildew. New varieties are being introduced every year and most are denoted with a "DMR" in the variety name to show it is resistant to the disease.
Those varieties with good resistance include:
- Amazel
- Prospera
- Prospera Compact
- Rutgers Devotion
- Rutgers Obsession
- Rutgers Passion
- Rutgers Thunderstruck
Several species and types have shown lower rates of basil downy mildew infection, including:
- purple leaf varieties
- lemon varieties
- varieties of hoary or lemon basil
Types
The basil family includes about 150 species from Asia, Africa, and South America. The species most commonly grown is sweet basil (Ocimum basilicum). Below are several cultivars, varieties, and species to try in your garden.
Sweet Basil (Ocimum basilicum)
Sweet basil is the most common type grown. It has white flowers and bright green, 2 to 3-inch-long leaves. Many different varieties and cultivars are available to gardeners. Common cultivars include:
- 'Genovese' | an Italian strain, regarded as the best variety for pesto and garlic dishes. Dark green leaves up to 2 inches long. Slow to bolt. Erect habit.
- 'Nufar' | resistant to Fusarium wilt
- 'Elidia' | compact habit and resistant to Fusarium wilt
- ‘Cardinal’ | very decorative dark purple flowers
- 'Magical Michael' | very uniform plants have ornamental flowers
- 'Emerald Tower | Compact upright habit
Purple Leaf
Grown for their ornamental foliage as well as their culinary uses. Soft lavender flowers. Popular cultivars include:
- ‘Dark Opal’
- 'Purple Ruffles'
- Red Rubin'
- ‘Amethyst’
- 'Aromatto' | bicolor leaf, green and purple
Bush or Greek
Dwarf varieties with very small, less than 1/2 inch long, pungent leaves. Sometimes called shrub basil. White flowers. Plants are excellent for edging or containers. Popular cultivars include:
- 'Fine Green'
- 'Green Bouquet'
- 'Spicy Globe'
- 'Pluto'
- var. minimum
Large or Lettuce Leaf
Large, wide leaves. Flavor is less pronounced than other green basil varieties, sometimes preferred for salads or sauces. Popular cultivars include:
- 'Mammoth'
- 'Napoletano'
- 'Green Ruffles'
- ‘Italian Large Leaf’
Scented
These basils possess flavors reminiscent of other plants. They can be used in recipes where a touch of a different flavor is desired. Often used in fruit preserves or in custards and sorbets. Common cultivars include:
- 'Licorice'
- 'Anise'
- 'Cinnamon'
- 'Clove'
- ‘Mrs Burns Lemon’
- 'Sweet Dani' (lemon scented)
Thai
A variety of sweet basil (Ocimum basilicum var. thyrsiflora), these cultivars are known for their narrow leaves, purple stems, and pinkish purple flowers. The scent/flavor is sweet, anise-like with hints of licorice, along with a slight spiciness not typical in cultivars like 'Genovese.' Popular cultivars include:
- 'Thai'
- 'Sweet Thai'
- 'Siam Queen'
Lemon Basil (Ocimum × africanum)
Also called hoary basil and Lao basil, this species is a hybrid between sweet basil (Ocimum basilicum) and American basil (Ocimum americanum). It is has leaves that are narrower than sweet basil with a serrated edge, white flowers, and a lemony scent. It is used in cooking.
Holy Basil (Ocimum tenuiflorum)
Plants with green or purple leaves on hairy stems and purplish flowers. Plants are used in some Thai cuisine, but this species has its most significant use in religious ceremonies and is a sacred plant in Hinduism. This plant is sometimes listed under O. sanctum, a previous name.
African Basil (Ocimum gratissimum)
Also called clove basil, plants grow tall and are heavily branched. Leaves are narrow and highly aromatic. Can be used in cooking and as an insect repellent.
American Basil (Ocimum americanum)
Despite its common name, this species is native to Africa and Asia. Leaves are hairy and have a citrus-like odor, giving it another common name of lime basil.
Camphor Basil (Ocimum kilimandscharicum)
Native to East Africa, this species is used more for medicinal purposes than culinary purposes. In garden settings, African blue basil is more common and a hybrid of this species and 'Dark Opal' sweet basil. This highly ornamental species has attractive purple leaves and lavender flowers that are highly attractive to pollinators.
Uses
Although basil is most famously linked to Italian cuisine, it’s a globally embraced herb. Its fresh or dried leaves are used in a wide variety of dishes, including soups, stews, sauces, salads, vegetables, and meat, fish, and egg preparations. Basil also flavors vinegars, teas, and oils.
It pairs especially well with tomatoes and is a staple in seasoning pizza, spaghetti sauce, sausage, soup, tomato juice, dressings, and salads. Basil is the key ingredient in pesto, where it’s blended with pine nuts, oil, and cheese. While commonly found in savory, peppery dishes, basil also makes appearances in fresh fruit desserts.
Purple basil is best enjoyed fresh, particularly in salads and for crafting flavored vinegars. In gardens, its vibrant color offers a striking contrast to other annuals and perennials. Both purple and green basil stems are visually appealing and can be used in floral arrangements.
Scented varieties like cinnamon and lemon basil bring unique flavor notes to special dishes. These delicately flavored basils are ideal for making jellies, jams, vinegars, and even sorbets.
Besides its edibility, basil is an aromatic herb and is often used in potpourri and sachets. The cosmetic industry uses basil oil in lotion, shampoo, perfume, and soap. As an ornamental in the flower garden, basil has attractive foliage and flowers.
History
The name basil may be derived from the Greek word basileus, meaning "king," or basilikon, meaning "royal." In Latin, basiliscus refers to the mythical basilisk—a fire-breathing dragon so repulsive it could kill with a glance. According to Roman legend, basil was believed to be the antidote to the basilisk’s venom. Its botanical name, Ocimum, comes from the Greek meaning "to be fragrant."
In 1600s England, basil was used both as a culinary flavoring and as an insecticide. People hung it in doorways to repel flies and ward off evil spirits. In Italy, basil became a symbol of love. A pot of basil placed on a balcony signaled that a woman was ready to receive her suitor, and if he brought a sprig of basil, she would fall in love with him. Young men also wore basil to show they had serious romantic intentions.
In India, basil held deep spiritual significance. Hindus believed that burying a basil leaf with the deceased would help them reach heaven, which contributed to the popularity of holy basil. It was also considered sacred to the gods Krishna and Vishnu.
In the 1800s, Europeans and Americans used it as a mild sedative by adding leaves to bath water, teas, and massage oils. It was traditionally preserved by air drying or layering with salt in earthenware crocks.
More Information
- Growing and Using Basil (PDF)
- Growing, Harvesting and Drying Herbs
- Growing Herbs Indoors
- Growing Herbs in Containers
- Ornamental Herbs for Iowa
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