Basil, the common name for Ocimum basilicum, is a popular sweet herb of the Mint Family esteemed for flavoring and formerly used for medicinal purposes. An annual of the tropics, it is tender and should not be attempted outdoors until the weather is warm.
Basil grows easily from seed which may be sown in the garden or started indoors. Basil also grows well indoors under fluorescent and HID plant growing lights.
The small flowers are white or purple, but the plant is grown for its sometimes purple tinged leaves, which are cut during the growing season and used fresh or dried in bundles.
Growing the Herb Basil
Plants should be transplanted or thinned to stand 6 to 10 inches apart; they prefer a quick draining, light soil in a warm location.
If the soil is rich, a plant cut back will develop successive crops of foliage until fall. At that time, roots of strong plants can be lifted and potted up to be moved indoors for a winter supply.
Although basil will grow best outdoors, it can be easily grown indoors in a container or hydroponic planter and, like most herbs, will do best on a south-facing windowsill (in the Northern Hemisphere). It should be kept away from any drafts, and must have plenty of sunlight, therefore a greenhouse or cold frame is ideal if available.
Basil plants whose leaves have wilted from lack of water will normally recover if they are watered thoroughly and immediately placed in a sunny location.
Basil can also be propagated very quickly and reliably from cuttings.
Leaf production slows or stops on any stem which flowers, so you should pinch off any flower stems to keep the plant in production, or pinch off some stems while leaving others to bloom for decoration or seeds. Once you do let the plant flower, it will produce seed pods containing small black seeds which you can save and plant the following year. Picking the leaves off the plant helps promote continuouse growth, largely because the plant responds by converting pairs of leaflets next to the topmost leaves into new stems.
Basil plants are easily grown and trimmed to form protective hedges.
Outdoors, containers (sow direct in final pots, or in plugs and later transplant to final pots), and hydroponics. Nighttime temperature must not go below 50° Fahrenheit or 10° Celsius.
Basil usually grows to a height of 12 to 18 inches (30 – 45cm).
Basil plants should be spaced between 9 and 12 inches (22 and 30 cm) apart.
Preferred pH Range
Basil will grow in a very wide pH range between 5.1 (strongly acidic) and 8.5 (alkaline) with a preferred range of 5.5 (strongly acidic) to 6.5 (mildly acidic).
Sow seed indoors before last frost or direct sow outdoors after last frost. Basil is easily propagated through herbaceous stem cuttings.
Seed Germination Period
Basil seeds will germinate in soil in approximately 5 to 10 days, but can germinate in as few as 2 or 3 days in dedicated propagation media such as Oasis Rootcubes, Rapid Rooters, or Grodan Stonewool.
Number of Seeds per Gram
There are between approximately 500 and 1,000 basil seeds per gram, depending on variety.
Basil prefers soils that are well drained, and average to rich in composition.
Alternative Growing Media
Soilless potting mixes (Pro-Mix, Sunshine Mix, etc.), perlite, vermiculite, rockwool, coco peat, Oasis Rootcubes.
Time From Seed to Saleable Plant
Seeds to finished plugs in approximately 8 weeks. Plugs to saleable plants in approximately 5 weeks.
Sun & Lighting Requirements
Basil grown outdoors prefers full sun.
Basil will grow indoors satisfactorily under standard fluorescent lamps, and exceptionally well under high output fluorescent grow lights, compact fluorescent, or high intensity discharge (metal halide or high pressure sodium) plant growing lights.
Keep standard fluorescent lamps between 2 and 4 inches from the tops of the plants, high output and compact fluorescents approximately one foot above the plants, and HID lights between 2 and 4 feet above the plants, depending on wattage.
Have an oscillating fan gently stir seedlings for at least 2 hours per day to stimulate a more compact, and sturdier plant habit.
Annual. Not applicable.
Water regularly, being careful not to overwater. Allow soil to go completely dry between watering, then soak thoroughly.
Potential Plant Pests and Diseases
Basil can be susceptible to whitefly, thrips, aphids, and Fusarium wilt.
Basil planted near tomatoes, peppers, oregano, asparagus, and petunias can help these plants repel or distract asparagus beetles, mosquitoes, thrips, and flies, and is said to make tomatoes taste better.
Planting chamomile or anise near basil is said to increase the essential oils of basil.
Basil is known to attract bees and butterflies and has very aromatic foliage.