When preserving herbs If harvesting the herbs from your own garden pick the herbs just before they flower for maximum flavor. Harvest herbs on the day that you plan to preserve them. Garden herbs, as well as store-bought herbs, should be thoroughly washed before storage. There are a number of ways you can then preserve the herbs for use in the kitchen later.

Drying

This method works well with rosemary, sage, thyme, oregano, and marjoram. Make bundles of 6-8 stems, tie them with twine or a rubber band and hang them in a warm place away from sunlight. Allow to dry until the leaves are crumbly (1-2 weeks usually). If you wish, you can remove the leaves from the stems at this point. Store the dried herbs in an air-tight container. They will be good for about a year.

If you don’t have a convenient place to hang herbs then you can dry them in an oven. Spread the herbs on a baking sheet covered with parchment paper and place in a 150º F. oven for about 1 hour or until completely dry. Store in an air-tight container.

If you have a food dehydrator then you can also use this for drying herbs. This could take up to 3 hours depending on the type of dryer.

Freezing in bags

Freezing is the best option for soft-textured herbs such as basil, cilantro, tarragon and parsley.  Simply place the herbs, after removing excess water, in zip-lock bags, squeeze out the air and store the bag in the freezer. They will be good for about a year.

Freezing basil in ice cubes is an option.

A convenient way to preserve herbs in small portions is to freeze in ice cubes. Chop the herbs up finely (either by hand or in a food-processor) and fill the wells in an ice cube tray about half full with herbs. Top up with water (or broth) and place in freezer.  The frozen blocks can be transferred to plastic bags for storage.

A variation on this procedure is to make a paste or pesto with olive oil to produce flavored ice cubes.  Macerate the leaves of herbs with the oil in a blender or food processor to form a thick paste. This can be frozen directly in plastic bags or, more conveniently for future use, in ice trays. Once frozen, the cubes can be stored in plastic bags. 

These two methods are also convenient for freezing mixtures of herbs suitable for specific recipes. For example, a blend for flavoring Italian dishes may consist of equal portions of basil, oregano, and rosemary.

Perserving Basil in salt from the American Herb Society:

Preserving in Oil & Salt, Basil can also be preserved by placing leaves in a jar over ½ inch of olive oil, layering the leaves with oil and a sprinkling of salt, and storing in the refrigerator. Individual basil leaves can be removed and used as needed. One problem with this method is the potential for botulism to develop, even in the refrigerator. For safety, do not keep oil longer than 2 weeks, or use another preservation method .

Leaves can also be preserved by layering in salt alone. Do this by layering sea salt and basil leaves in a glass pint jar with a plastic lid and storing in the refrigerator. Leaves will stay fresh and last until the next harvest season. Salt can then be used in soups and sauces or sprinkled over vegetables.

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- Courtesy of NYBG Plant Information Service