Harvest the herbs that you want to dry and do not wash them as this may encourage the developing of moulds. Dry the herbs in a warm, dry place by hanging them upside-down if you are using whole shoots or if you are using only leaves, flowerheads or petals, place them in a single layer on a rack covered with netting, muslin or kitchen paper and leave them in a warm, dark, well-ventilated place until they become crisp.
For drying the herbs in a microwave you will have to wash them and pat them dry then place sprigs or leaves in a single layer on kitchen paper. Microwave them for 2-3 minutes but check them every 30 seconds to see if they need to be rearranged to ensure even drying. Cool and crumble them then store them as air-dried herbs.
In summer or early autumn, cut the seedheads as they turn brown, place them in a paper bag or hang them upside-down and cover them with muslin to hold the seeds as they dry and fall off from the seedheads. Place them in a warm, dry place to ripen and when they are dry remove the seeds and store them. If you will want to use some of the seeds for sowing then keep those seeds in a cool, dry, frost-free place.
Most of the roots are best used fresh but some of them may be dried and ground. Harvest the roots, wash them thoroughly, peel them, chop or slice them then spread them on an absorbent paper and dry them in a cool oven or a warm airing cupboard at 50-60 Celsius degrees (122-140 F) until brittle. Crush or grind then store them for later use.
For this method, pack whole sprigs into plastic bags and freeze them. For long-term storage, blanch them before freezing by dipping them in boiling water then in iced water. Pat dry and freeze. This method is used for many soft-leaved herbs like basil and parsley in order to retain their color and flavor better.
Freezing in ice
An other way to freeze some herbs like borage flowers and mint leaves is to freeze them in ice cubes so that they can be used as a decorative addition to drinks, as ice protects the herbs from damage during storage. Herbs used for cooking should be chopped before freezing. In ice cube trays, add one tablespoon of water to one tablespoon of chopped herbs. Place the ice cubes in a sieve and drain the water before use.
Thyme, oregano, french tarragon and lavender are some of the herbs that have their flavor preserved by being steeped in vinegar. For this method, lightly crush some fresh herbs and loosely fill a clear glass jar with them. Warm wine or cider vinegar and pour it over the herbs then seal the jar. Leave the jar in a sunny place for 4 weeks, shaking or stirring it daily. For a stronger flavor replace the herbs and leave the herb vinegar for two more weeks. Strain and bottle adding a fresh sprig of the herb for identification.
The most used plant for being preserved in jars of oil is basil, as the leaves themselves may then be used in different cooked dishes or sauces. It is not recommended to make your own herb-flavored oils, because there is a risk of botulism.