Holy basil (Ocimum sanctum) is closely related to the sweet basil you put into your spaghetti sauce. Called Tulsi in India, Ayurvedic practitioners have used it for centuries to treat a wide assortment of diseases, from headaches to cancer. It is classed as an adaptogen, meaning that it is good for whatever ails you. A 1991 study with animals (Indian Journal of Pharmacology) showed it to be a powerful anti-stress agent, better than Asian or Siberian ginseng. This clove-scented herb is easy to grow and often self-sows, giving you a new crop the following spring.
Wait until your plant(s) flower because the flowers hold more of the potent essential oils than the leaves. When flower spikes form, snip them off down to their base; the plant will continue to send up more flower spikes from the area you cut. It's fine to include some leaves as well as the flowering tops.
Tie small bunches of the flower spikes at their base with string or twine. Then hang them in a warm, dark, dry, well-ventilated area such as a garage clothesline.
Alternatively, spread your cut flower spikes on an old window screen that you prop up on a table with bricks or pieces of wood.
Check your holy basil every day to monitor its drying progress. When it feels crunchy, take it down and strip the dried foliage off the stems. Depending on the weather, this will happen within 1 week or less.
Store your dried holy basil in tightly sealed glass jars or plastic zipper bags, which you can keep in your refrigerator or freezer to ensure freshness.