Fresh herbs bring a welcome hint of summer, and many favorites thrive on a windowsill in winter as well as in the summer garden.
Most herbs require four to six hours of sun or 14 hours of supplemental light daily, and a south or southwest exposure is best. All herbs except basil perform best next to a cool windowpane. Many herbs, such as thyme, chives, oregano, and rosemary, can be grown on the dry side. Make sure pots drain well, and pinch plants frequently to keep windowsill herbs stocky and attractive.
Some herbs are easily started from seed, while others are best started from cuttings or divisions. Basil, parsley, and cilantro perform best indoors when grown from seed. Using medium-weight sterile potting mix, cover with milled sphagnum moss and water. Covering pots with a plastic bag or glass plate keeps seeds moist for germination. Seed-grown herbs won't produce large plants, but the young plants are just as tasty and can be harvested within a couple of weeks. Seeding heavily, fertilizing, and pinching regularly will provide plentiful herbs all winter long.
If you have a thriving outdoor herb garden, you can also pot up divisions to bring inside for the winter. Divide and pot sage, oregano, lemon balm, mint, and thyme about three weeks before the first frost. Dig entire plants of annual herbs such as rosemary to bring indoors. Once you have potted up a division into sterile potting soil, tie an old nylon or piece of cheesecloth around the pot and the plant base to keep insects from entering the pot, and find a protected spot for the pot until it's time to bring it in. The foliage that most herbs grow outdoors will not survive indoors, so cut it back almost to the base. (Rosemary, bay, chives and thyme, however, should not be cut back.)
When you bring the herbs in to the windowsill, watch for insects, especially aphids and spider mites. If you detect a problem, spray the plant with tepid water or submerge it for 15 minutes. Use insecticidal soap for severe problems, but avoid harsh chemicals.
Some excellent candidates for windowsill growing are thyme, lemon thyme, sage, oregano, basil, parsley, and chives. Consider chamomile, lavender, lemon balm, and mint, too. Herbs can make your windowsill a spot not only for flavor but for fragrance as well.