The shelf life of many herbs is one to two years but this period is shorter when herbs are exposed to light, heat and open air. Herb leaves keep their flavor best when they are stored whole and crushed just before use. When herb seeds are to be used for cooking, the seeds should be stored whole and ground up as needed.
To prepare plants for drying, remove blossoms from the herb plant and rinse the leaves on the stem in cold water to remove soil. Allow plants to drain on absorbent towels until dry. Then place the herbs in a paper bag and tie the stems. Leave 1 to 2 inches of the stems exposed. This allows the plant oil to flow from the stems to the leaves. Place the bag in a warm, dry location. In about one to two weeks, when the leaves become brittle, tap them free of the stems and the leaves will fall into the bag. Store leaves in an airtight container away from the light.
Clean herbs as for bag drying but the heavy stalks can be discarded. Put the leafed stems one layer deep on a tray in a dark, ventilated room. Turn over the herbs occasionally for uniform drying. The leaves are ready for storage when they are dry and the stems are tough.
If you have a microwave oven, you can use it to dry herbs. Place the herbs between paper towels and set them on the rack. Close the door and turn the oven on a medium setting for about 2-3 minutes. Then check for dryness; the leaves should feel brittle and should crumble easily. If they are not done, turn the oven on for 30 seconds longer. Although this process actually cooks the herbs, the end product is just about the same as air drying. Store the dried herbs in closed containers.
Herbs may also be frozen. Rinse herbs in cold water and blanch in boiling, unsalted water for 50 seconds. Cool quickly in ice water, package and freeze. Dill, parsley, chives and basil can be frozen without blanching.
Rosemary (Rosmarinus officinalis) is widely used as a culinary herb, especially in Mediterranean dishes, and is also used as a fragrant additive in soaps and other cosmetics. Traditionally, rosemary has been used by herbalists to improve memory, relieve muscle pain and spasm, stimulate hair growth, and support the circulatory and nervous systems. It is also believed to affect the menstrual cycle, act as an abortifacient (inducing miscarriage), relieve menstrual cramps, increase urine flow, and reduce kidney pain (for example, from kidney stones). Recently, rosemary has been the object of laboratory and animal studies investigating its potential in the prevention of cancer and its antibacterial properties.