As seen in the descriptions of the wild species above, one or more parts of an herb may be of medicinal value. Most commonly, leaves are taken, but depending on the herb, flowers, seeds, bulbs or roots may also be useful. Information on which parts of the plant have medicinal benefits can be found in herbals. Below are the points to consider when harvesting. These rules apply to harvesting in the wild as well as the herb garden
As a general rule, herbs are best harvested when they have developed maximum amounts of essential oils. For many herbs, that is the time when the flower buds are just starting to open. However, mint is richest in essential oils when its flowers are in full bloom. During the harvest season, wait for a day that is neither too hot nor too cold. Skies should be blue. After a period of rain let at least one sunny day go by
Time of Day
Plant parts growing above ground have the most juice in the morning. Therefore, harvest leaves and flowers in the late morning, after the dew has dried off. Roots are juiciest at night and should be harvested in the evening before night moisture develops.
Amount of Harvest
Do not take more than ten percent of each plant if you want to keep it healthy and productive throughout the season.
This rule is true for garden or wild herbs. Taking more can be a severe shock to a plant. Conversely, the pruning effect of careful harvesting can strengthen a plant and make it grow sturdier. Never harvest more than can be used or dried at one time. At the end of the season, garden perennials can be cut to about half their height, while annuals can be cut down to the ground.
During their harvest, plants should not be put into bags but kept in airy containers, such as baskets, for good circulation. Crushing or breaking should be avoided because it diminishes the value of the plant by destroying some of its essential oils. Once inside, herbs should quickly be washed in cool water, spread on towels and gently patted with a towel until all moisture is gone
For leaves, only the young growth of the parent plant should be taken. Leaves that are damaged by insects or otherwise imperfect should be discarded. Herb flowers such as camomile, calendula, borage and chives should be picked when they are fully opened. However, lavender should be taken when it is just starting to open. Do not take flowers that are old or damaged in any way. Bulbs, such as onions or garlic, should be harvested when their leaves are starting to die, usually in late summer or early fall.
Seeds have to be closely watched for proper harvesting. No trace of green should be left on seeds. If there are seed pods, they should be very dry. To avoid losing too many seeds while harvesting from certain plants, put a paper bag over the seed head, cut the stalk gently and then immediately turn it upside-down to let any seeds fall inside the bag. Seed heads should be kept inside the paper bag and put in a very warm, airy place for a few days until thoroughly dry. Bags can then be shaken until all seeds have come loose. Seeds should be kept in dark, airtight containers, preferably glass and never metal. Seeds to be planted in the following year should be kept cool or even frozen.
Drying, the removal of moisture from plants, will prevent the growth of fungi and bacteria. Bacteria grow well on plants with a water content of forty to forty-five percent while fungi need fifteen to twenty percent moisture. Although thorough drying is necessary, plants are not supposed to lose every last trace of moisture during the drying process. Herbs would become brittle and crumble into dust if all their moisture were removed. Properly dried medicinal herbs will have a moisture content of about ten percent. Some herbs and plant parts are so high in moisture, that they have to be dried with a heat source. This is true for most seeds and all roots, stems, bark, fruit, berries and for all water-retaining plants, such as mullein (Verbascum thrapsus), camomile flowers (Matricaria chamomilla) and dead nettle (Lamium). If extra heat were not present, the herbs would be attacked by bacteria or fungi before having a chance to dry properly. During or after drying, plants should not be handled any more. Dried herbs should never be mixed with fresh ones.
The best method of producing dried herbs is to keep plants in an airy room, away from sunlight at temperatures between 70°-600°F (20°-320°C). Herbs containing essential oils should be dried below 570°F (300°C) to preserve their volatile oils. Herbs to be dried are sorted and cleaned well. All damaged parts are discarded. Strongly aromatic herbs are dried separately. Flowers, such as camomile, arnica and poppy, have to be dried quickly and kept away from light. Leaves or flowers are spread on linen cloths or non-wire mesh frames to allow for air circulation. Drying whole green plants takes about a week; the crisp leaves are then removed from their stems and put into airtight containers. If the whole plant is of medicinal value, it is chopped into very small pieces and then stored in airtight containers.
Containers should be opened after one or two days of storage to check whether herbs are really dry. If there is any condensation, take herbs from the container and spread them out to dry some more. If this is not done, herbs will spoil. If there is enough room for storage, whole plants should be stored without cutting them up. Similar to the practice of grinding only small amounts of coffee beans at a time, whole herbs are best when chopped as needed. Unlike green plants and flowers which must be kept away from sunlight, roots and bark can be dried in the sun. They are cleaned of any soil, washed quickly, cut lengthwise and then chopped into fine pieces. They can be spread out on linen cloths or on non-wire mesh frames.
Drying Herbs in Bunches
Non-succulent plants can be dried hanging upside-down in bunches. This method may look romantic, but it has its problems. First of all, when done in a kitchen, too much moisture may spoil the herbs. In addition, drying in bunches will take longer than individual drying so that dust could settle on the herbs. If drying in bunches is attempted, it should be done in a dry, airy room without direct sunlight. Windows should be closed at night and during early morning hours to prevent moisture from entering the room. Herbs cannot be dried in rooms with a cement floor. To prevent dust from settling and to keep out light, herb bunches can becovered with wide paper bags that are open at the bottom.
Herbs can also be dried on cookie sheets in an oven set to between 230-265°F (110°-130°C).
Herbs can also be dried in a day or two with the aid of a food dehydrator. The latter method is preferable to oven drying since it seems to retain more of the herbs color and flavor.
After herbs are dried, they should be put in dry, dark, airtight containers, preferably opaque glass jars. Metal containers should never be used. Herbs should be clearly labeled with their names and the dates of harvest. Do not store herbs in moist places such as the kitchen or a bathroom. Herbs should not be kept for more than one season. As new herbs replace old ones each year, any leftovers can be used in herbal baths. You can also use some of your herbs in sachets and potpourris