- Traditional sweet basil is the most popular variety, used mostly for cooking.
- Sow seeds directly into the ground after the danger of frost has passed.
- Harvest at any time by snipping fresh young leaves as needed.
- You can dry or freeze basil to use when fresh basil is unavailable.
One of the easiest and most popular culinary herbs to grow is the common or sweet basil, Ocimum basilicum. A member of the mint family (Lamiaceae), it is native to southern Asia and islands of the South Pacific. This tender annual is popular for its aromatic leaves, used fresh or dried. Basil seeds are common in Thai foods.
Like most herbs, basil requires a sunny location that receives at least six to eight hours of bright light per day and well-drained soil conditions.
Soil pH and fertility
- Have your soil tested.
- A pH range of 6.0 to 7.5 is best.
- Fertilize sparingly, using a 5-10-5 commercial fertilizer once or twice during the growing season at the rate of 3 oz. per every 10 ft. of row.
- Use a liquid fertilizer at one-half the label recommended strength every four to six weeks for indoor plants and every three to four weeks for basil grown outside in containers.
Traditional sweet basil, Ocimum basilicum, is the most popular variety, used primarily for culinary purposes such as pesto and tomato dishes. There are many other varieties offering both ornamental value and unique fragrances. Due to the emergence of basil downy mildew, it is important to choose a variety resistant to this disease.
- Spicy Globe basil - O. basilicum, 8"-10". Use green foliage in many dishes as well as a nice edging or border because of small, compact plant size. This is a good indoor plant as it is slower to go to seed than most other types.
- Lettuce Leaf basil - O. crispum, 15". Produces large, crinkled green leaves that have a sweeter flavor than other varieties. Very vigorous grower.
- Lemon basil - O.b. 'Citriodorum', 12"-18". Fine-leafed plant with distinct lemon fragrance. Use in potpourri, iced teas, salads.
- Opal basil - O.b. ‘Purpurascens', 12"-18". A very versatile variety that has red-purplish foliage and pink flowers. Use ornamentally in most garden settings, fresh floral arrangements or herb vinegars. O.b. 'Minimum' is a compact variety.
- Cinnamon basil - Ocimum sp., 18". This variety offers dark green shiny leaves and pink flowers. The flavor and fragrance in both foliage and flowers is very spicy. Use in dried arrangements, potpourri, vinegars and jellies.
- Thai basil - O.b., 24"-36". An upright, well-branched plant with flavor and fragrance distinctly different from other basils. Excellent for Asian cuisine. Highly decorative with purple stems and flowers.
- Sow seeds directly into the ground after danger of spring frosts has passed.
- Sow evenly, covering with one-fourth of an inch of soil. Keep moist and free of weeds.
- Seeds should germinate within five to seven days. The basil seedling is recognizable by its two broad seed leaves, each shaped like a capital D, borne with flat sides facing each other.
- Thin and transplant seedlings to stand 6-12 inches apart once they have developed two to three pairs of true leaves.
- A two to three inch mulch of grass clippings, straw, compost or ground-up leaves retains soil moisture and minimizes weeds around the plants.
Sow seeds indoors six to eight weeks before planting outside to get a head start on the growing season. This is especially beneficial for some of the slower-germinating varieties such as O.b. 'Purple Ruffles.'
How to keep your basil healthy and productive
- Depending on the amount of regular rainfall, water deeply every seven to ten days to insure the roots are receiving enough moisture.
- Plants grown in containers will dry out faster than those in garden beds. Water them more frequently.
- Choose a container with holes in the bottom for proper drainage.
- Since basil is a tender annual, it will not survive the winter in our region.
- At the end of the growing season, you may choose to dig up your plants and bring them inside for the winter. If this is the case, make sure they receive plenty of bright light. You may have to install artificial lights and run them for 10-12 hours daily since indoor light will not be enough during the darker winter months.
- As annuals, basil plants will flower and die eventually, even indoors. Plan to start new seeds or buy new plants each spring.
- It is important to prune the plant periodically throughout the growing season to maintain succulent and productive growth.
- If you allow basil to flower and form seed, it will become woody and yields will be considerably less. Flowering will lead to more bitter flavors.
- Some of the flowers have ornamental value, especially the purple-leafed varieties which have pink blooms.
- If your plants flower, cut some stems for a mixed bouquet.
Begin harvesting at any time by snipping the fresh young leaves as needed. If you harvest whole stems, cut just above a pair of leaves. New growth will occur at the cut point and should be visible within a week's time.
Fresh basil is best. The clove-like aroma and flavor is a wonderful seasoning in both Western and Asian foods. The fresh leaves have a tender texture.
Many people use dried or frozen basil during the cold months when fresh basil is unavailable.
- Preserve leaves by hanging the foliage upside down in small bunches. Air dry in a warm, dry, well-ventilated room for a week.
- You can also dry foliage by spreading leaves flat on a drying rack under the same conditions.
- Once thoroughly dried, strip the leaves from the stems and store whole or ground in an airtight container away from heat sources and bright light.
- If stored properly, dried basil should keep for about a year.
- If any sign of moisture occurs, empty the container and repeat the drying process.
- Basil leaves turn an unpleasant brown color when air-dried. Freezing is a better method.
- Freezing is another method of preserving basil and usually results in a product with a flavor more like fresh basil.
- Freeze whole leaves in small quantities in small plastic bags or chop up the leaves into small pieces and place them in an ice cube tray topped off with a little water.
- You can also mix one-fourth-cup chopped basil with two teaspoons of vegetable or olive oil. Drop teaspoonfuls of this mixture onto wax paper-lined baking sheets and freeze. Peel off the wax paper and store the basil mixture in plastic bags.
- Similarly, prepare basil pesto in quantity, and then freeze in small containers. Omit any cheese from the recipe if you plan to freeze pesto.
- Whichever method you choose, use frozen basil within a year.
Managing pests, diseases, and disorders
Many things can affect basil plants. Changes in physical appearance and plant health can be caused by the environment, plant diseases, insects and wildlife. In order to address what you’re seeing, it is important to make a correct diagnosis.
You can find additional help identifying common pest problems by using the online diagnostic tools or by sending a sample to the UMN Plant Disease Diagnostic Clinic. You can use Ask a Master Gardener to share pictures and get input.
The most common basil issue in Minnesota is Basil downy mildew. This disease causes fluffy growths on the underside of leaves and can kill entire plants.
Reviewed in 2022