Wash the rosemary in cold water and dry it carefully with paper towels. Then place it in a plastic bag or in an airtight container lined with absorbent paper. Keep it in the refrigerator for a period of 5 to 7 days. You can also freeze rosemary. Wash it carefully, dry it and finely chop it. Place it in a freezing bag, press the air and seal it. You can then keep the sachets in the freezer for several months. This method works better for rosemary. Wash rosemary and dry it carefully. Tie it into small boots and hang it backwards in a dry and well ventilated place. Once the leaves are dry and brittle, remove them from stems and store them in an airtight container. This method is useful if you want to use rosemary to flavor olive oil. Wash rosemary and dry it carefully. Then place it in a bottle of olive oil and keep it in a cool and dark place for one to two weeks.