Americans may not consider basil the passport to paradise like the Hindus of India, or the token of love like the Italians, but many gardeners do consider it a vital herb for flavoring tomato dishes. This tender annual must be replanted yearly, as basil completes its life cycle and dies off each year. But, with attention to replanting before the old plant matures, you can grow basil in a windowsill herb garden throughout the year.
Plant basil in loose, lightweight soil. A mixture of one part potting soil, one part perlite and one part peat moss makes a suitable soil for growing basil. The University of Illinois Extension Office recommends placing an inch of gravel in the bottom of the pot to promote good drainage.
Place basil plants in a sunny southern or western window. Herbs require direct sunlight to grow and develop the oils responsible for their flavor and fragrance.The University of Minnesota Extension recommends using a plant light or lamp for 10 to 12 hours a day during the dark winter months.
Water when the soil feels try to the touch an inch below the surface of the soil. Check soil moisture by inserting your finger into the soil. During active growth basil may require frequent watering, perhaps as often as every few days. During the winter when growth has slowed, watering once a week is typically adequate.
Place basil plants on a pebble tray filled with an inch or two of water to increase the humidity around your plants. The West Virginia University Extension Office also suggests misting plants regularly.
Fertilize basil sparingly. A weak solution of water-soluble fertilizer mixed to 1/4 to 1/2 strength applied once a month during active growth provides the nutrients basil needs. Herb flavor and aroma may be inhibited by too much fertilizer.
Pinch out the center leaves at the ends of branches to encourage your basil plant to form compact foliage. Pinching forces the plant to send out new branches along the stem and creates dense foliage.
Snip off outside leaves as needed for your culinary use.
Plant basil seeds in early spring to replace older plants. Although seeds can be planted during the winter, without the use of plant lights, seedlings will become tall and spindly. Light from the window is inadequate for seed starting during the dark winter months.