Basil is one of the most popular herbs grown in gardens all over the world. From the rich, licorice laden taste of Thai Basil like Siam Queen Basil to the classic flavor of Italian Large Leaf Basil. Basil is also one of the easiest herbs to grow if you learn a few simple steps.

How to Sow and Plant

Basil may be grown from seed sown indoors and transplanted outside after your last frost date or sown directly in the garden once soil temperature has reached 60 degrees F. Basil plants can also be kept as potted specimens, either indoors or outdoors.

Sowing Seeds Indoors

Sow basil seeds indoors 6-8 weeks before the last frost in spring

Sow basil seeds ¼ inches deep in seed-starting formula

Keep the soil evenly moist at 70 degrees F

Seedlings emerge in 7-14 days

As soon as basil seedlings emerge, provide plenty of natural light on a sunny windowsill or grow under fluorescent light on a 12 hours cycle.

Transplant basil plants in the garden after a period of “hardening”, increasing the seedling’s exposure to sunlight gradually over a one-week period. Seedlings are ready for transplants when they have 3 to 4 true leaves.  

Do not expose basil plants or seedlings to frost.

Sowing Seeds Outdoors

Direct sow in average soil in full sun after all danger of frost has passed when the soil temperature is at least 60 degrees F. Basil grows best in fine, well-draining soil of average fertility.

Sow basil seeds evenly and cover with ¼ inches of fine soil.

Firm the soil lightly and keep evenly moist.

Seedlings will emerge in 7-14 days, possibly longer in cooler soils.

How to Grow

Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients. Mulching the growing area helps the soil retain moisture and prevents weed seeds from germinating.

For basil, an organic mulch of aged bark, weed-seed free straw or shredded leaves is ideal. Mulching has many benefits including added organic matter and fertility as it will improve the soil as mulch breaks down in time. Always keep mulches off a plant’s stems to prevent possible rot.

Keep basil plants well-watered during the growing season, especially during dry spells. Keep the soil moist but not saturated. Basil plants should not be allowed to dry out.

Do not harvest too much of the plant at one time as this may weaken the plant.

Growing Tips

Pinch leaves from the tips of the stems as needed starting 60-90 days after the seedlings have two sets of leaves to encourage bushiness and increase the leave yield. Pinch the flowering stems as they appear to prolong the harvest.

Pick early in the morning for highest oil content. The highest quality basil is harvested just before flowering.

Flowers are also edible and may be used as a garnish.

Preserving Basil

To dry basil leaves, cut whole stems on a dry morning. Tie stems loosely together in small bunches and hang in a dry, airy location out of the sun. Basil may also be dried on a cheesecloth or a window screen in a dry, shady location. When thoroughly dry, store in a tightly sealed glass jar in a dry, dark location. 

Basil can also be frozen. Clean leaves can be frozen on a cookie sheet then placed in a sealed freezer bag. Another great preservation method is to mince the basil leaves and mix them with olive oil, then freeze the mixture in ice cube tray. The cubes can then be transferred to a sealed bag and kept for up to 8 months in the freezer.  

Common Disease and Problems

These are common diseases, pest and problem encountered by gardeners when attempting to grow basil.

Bacterial Leaf Spot

Causes: Soil born bacteria get into contact with the plant by water splashing during watering or rain events.

Symptoms: Brown or black spot that appear on the bottom of basil leaves and streaking of the same color on the stems. Diseased leaves die and fall off. If the infection is severe on the main stem the plant may die. The condition thrives in high humidity and cooler temperatures.

Solution: To prevent Bacterial Leaf Spot avoid planting basil in the same location in the future. Applying mulch to prevent water from the soil to splash to the underside of the leaves during watering can be of tremendous help. Do not use overhead watering if possible.

Botrytis Blight

Symptoms: Also called gray mold, this disease causes a brown to gray fungus to spread on plant leaves and stems.

Causes: Soil born fungus is naturally present.

Solution: Remove infected plants and plant debris, clean tool before and after working with diseased plants. Ensure good air circulation between plants.

Downy Mildew

Symptoms: Leaves turn yellow around the middle vein as the disease spreads, eventually turning grayish purple and fuzzy.

Causes: Naturally present and airborne pathogen. The condition thrives in humid conditions.

Solutions: Remove infected plants and plant debris, clean tool before and after working with diseased plants. Ensure good air circulation between plants.

Fusarium Wilt

Symptoms: Stunted and wilted plants and yellowish leaves. Brown streaks may occur on the stems. Later signs of the disease are twisted stems and leaf drop. The stem tissue is discolored.

Causes: Soil borne fungal disease that is commonly present in garden soil.

Solutions: Avoid waterlogging and make sure the soil is freely draining. Plant in containers.

Root-Knot Nematodes

Symptoms: Poorly performing plants. Wilting and poor growth in newly and established plants.

Causes: Classified as either a disease or pest, nematodes are microscopic worms feeding on the roots and may cause what looks like a nutrient deficiency, wilting and poor growth.

Solutions: Avoid planting in the same area as the nematodes are difficult to eradicate. Plant in containers. Introduce beneficial nematodes with predatory behavior.

Aphids

Symptoms: Greenish, red, black or peach colored sucking insects that can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants.

Causes: Insect infestation.

Solution: Introduce beneficial insects. Create beneficial insect habitat in and around your garden. Ladybugs are a well-known predator of aphids.

Japanese Beetles

Symptoms: Large beetles present on the foliage causing defoliation by feeding.

Causes: Insect infestation:

Solution: Hand pick early in the morning into a bucket of soapy water.

Slugs

Symptoms: Leave large holes in the foliage or leaves missing entirely. Slime trail left on leaves and stems. Slugs cause defoliation and can kill young plants with intense feeding. They mostly feed at night. Moist weather increases their presence.

Causes: Pest infestation.

Solution: Hand pick, at night if possible. Use slug traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent of cornmeal, but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.

Common Problems

Plants die after blooming

This is normal. Basil is an annual plant that will stop producing after it produces seeds. Pinch off the flowers before they set seed to prolong the life of the plant.

Leaves turn black overnight

Cold exposure. Basil is very sensitive to cold temperatures and will turn black with any frost.

Bitter tasting basil

This happens when the plants start flowering. At this stage the plants will no longer be productive.