Prized for its fragrant foliage and dainty violet, pink or white flowers, tulsi (Ocimum tenuiflorum, syn. O. sanctum) is widely grown as both a culinary herb and ornamental plant. Perennial in U.S. Department of Agriculture plant hardiness zones 10b through 11, it matures into a 2- to 3-foot-tall bush covered in slender, gray-tinged leaves. Tulsi grows equally well in containers and in the ground, although container-grown specimens are often smaller and shorter-lived than those grown in a garden. Both have similar growing requirements with several climate-related differences.
Things You'll Need
- pH meter or test strips
- Compost or potting soil with perlite
- Tape measure or ruler
- Disposable measuring spoons
- 15-15-15 or 7-9-5 water-soluble fertilizer
- 1-gallon container
- Pruning shears
- Rubbing alcohol
- Watch, clock or timer
- Measuring cups
- Dish soap
- Spray bottle
- 8- to 16-inch clay pot (optional)
Grow tulsi in moderately fertile, fast-draining soil with a pH of 6.1 to 7.5, which is in the neutral range. Amend heavy, clay-based soil and porous, sandy soil with a 2-inch-thick layer of compost to improve drainage and moisture retention. If you're growing tulsi in a pot, use standard potting soil that contains perlite.
Locate tulsi where it receives at least six hours of direct sunlight daily, placing it in a south-facing garden or near a south-facing window if growing it indoors. Provide light shade during the hottest part of the day if your climate is very hot and dry or the leaves show signs of scorching. Space multiple plants 24 to 36 inches apart.
Water tulsi deeply but infrequently to prevent soil-borne fungal infections. Run water at the base of a garden-grown plant until the top 2 inches of soil are very moist. Water container-grown plants until the soil is saturated and excess moisture trickles from the pot. Let the top half inch of soil dry out between waterings.
Reduce watering by half in winter to help prevent diseases. Let the soil dry out completely between waterings and avoid watering garden-grown tulsi if rain fell the previous week. Moisten the top inch of soil if the plant shows signs of wilting, but continue to let the soil dry out between waterings.
Feed tulsi biweekly from midspring till midsummer during the active growing season by dissolving 1/2 teaspoon of water-soluble fertilizer in 1 gallon of water and replacing one watering every two weeks with the solution. Use general-purpose 15-15-15 fertilizer if you grow tulsi for culinary purposes or use a bloom-promoting 7-9-5 ratio if you grow the plant as an ornamental.
Withhold all supplemental fertilizing from late summer until the following spring when growing tulsi outdoors. Reduce feeding by half during the winter months if growing tulsi in a pot. Cease feeding entirely until spring if your plant produces an excess of spindly growth.
Prune tulsi as needed year-round to control its size and promote a bushier, more-compact appearance. Before pruning the plant, soak the blades of your pruning shears in a solution of half rubbing alcohol and half water for five minutes to kill pathogens. Remove no more than half the stem growth when pruning.
Examine the undersides of the plant’s leaves for the presence of small, whitish insects, which may be a sign of whitefly infestation. Treat whiteflies by spraying the plant liberally with insecticidal soap and repeating the application every seven to 10 days until the infestation subsides. To make your own 2-percent-strength insecticidal soap solution, add 2 teaspoons of mild dish soap and 1 pint of water to a plastic spray bottle and shake well to mix.
Watch for symptoms of root infections, such as a wilted appearance, yellow foliage or dieback at the stem tips, and discard all affected plants to prevent the spread of pathogens to other plants. To head off root infections, grow tulsi in a suitably fast-draining site and spread a 1-inch-thick layer of mulch around each plant to reduce the need for watering.
Move container-grown tulsi indoors in autumn if you live in USDA zone 10a or below, placing the plant near a sunny window where the temperature stays consistently above 65 degrees Fahrenheit. In spring, move the plant to a sheltered location in the garden two weeks after the average last frost date in your area to allow it to reacclimate to outdoor humidity and light levels.
Repot container-grown tulsi in fresh potting soil each year. Depending on the plant's size, use an 8- to 16-inch clay pot with at least two bottom drainage holes.