Harvesting, Drying and Storing Herbs
There are still lots of research into the effects of several factors like growth cycle, daily rhythms and climate on the biochemical composition of medicinal plants. The active constituents of medicinal plants are found at different levels at different times of the day, month and growth cycle.
In general however, the amount of active constituents is highest at the end of the period of most active growth. Thus, plants should be harvested or collected just before opening into blossom i.e. leaves are to be collected just as flowers are beginning to open [1,2]. The condition ideal for collecting would be a day without rain which has been sunny from daybreak. This is because even though some leaves can rapidly dry after the rain, others like the Horehound can still retain its moisture and can easily develop mould and become spoilt if they were allowed to be massed together before drying. Excessive heat on the other hand can dry up the oil in the leaves.Underground parts on the other hand, have to be collected as the aerial parts die down. Leaves, flowers of fruits should never be collected when covered with dew or rain. Barks are usually collected after a period of damp weather because they separate most readily from the wood.
A good guide indicates that only the best shaped greenest leaves should be collected and withered, insect bitten or stained ones should be discarded.
When collecting leaves and herbs, they should be cut with a sharp knife or secateurs so as to avoid damaging the tender plant stems if one were to pull them off my hand. Pulling by hand not only can cause damage to the tender stems, it can also result in delay in new growth as well as encourage the entry of fungus or insects into the damaged tissue.
In areas of roadsides and high waste soil, it is important to pick only from the places free from excessive traffic. It is also vital to avoid fields sprayed with chemicals because chemicals can seep and infuse into the medicinal plants. Thoroughly investigating fields, woodlands and hedges that surround organic farms with the owner’s permission are important if there are no unpolluted areas within your vicinity to gather herbs from.
For example, when collecting Senna leaf, the official monographs allow for a certain percentage of stalks to be present in the mixture as it is difficult to get leaves, flowers or fruits that are free from other plant parts.
How the fresh plants are preserved by drying and appropriate correct storage.
Slow drying at moderate heat is important if one wants to promote or encourage enzymatic action. Drugs with volatile oils need to be dried and the oil to be distilled from them immediately because otherwise they can lose their aroma very easily. Furthermore, moist drugs can readily develop mould if not dried immediately. Drying apparatus and stills need to be readily accessible and as close to the growing plants as possible.
The duration of drying can vary between a few hours to many weeks and in the case of open-air drying, it is largely reliant on weather. Rapidly drying flowers and leaves help retain their aroma but the temperature used in each individual scenario needs to be governed by the constituents and physical nature of the drug. As a general guideline, Barks and Roots need to be dried between 30 and 65 degrees Celsius whereas leaves, herb and flowers may be dried between 20 and 40 degrees Celsius.
Herbs are spread in loose single layers on flat drying surfaces. One can use wire cooling racks from the kitchen because these can allow for air circulation and thus quicker drying. The time required for drying varies upon the herb and environment thus it is important to check the herbs often and turn them as needed to ensure even drying.
Roots are tricky to dry as they are usually very damp when harvested from underground especially since collecting is usually done in autumn when the soil is muddy and sticky. Roots must not be dug up for medicine when the leaves are still in full growth because they have not reached their full medicinal content levels. All efforts need to be made to ensure the entire root is dug up so a long spade or fork is required for this purpose. Scrape all the mud off the root, thoroughly wash and scrub them. Cut off the top stems and rootlets and large roots like the Burdock and Liquorice should be sliced to hasten drying.
Spread these out on shelves so they do not touch or they can be tied singly on strings in a warm shed or greenhouse for about 10 days, making sure to turn and inspect them daily. Once these roots have shrunk to around ¾ of their weight from drying, they can be finished by storing them above a stove or in a cool oven for another 10 days depending on the moisture levels in the atmosphere. Roots are dry once they are brittle.
To dry bulbs and corms, tie them up in small bunches like onions, in a shed. Keep a close watch on them to ensure even drying is obtained.
Long storage is usually not recommended except in a few unique cases such as cascara bark because the combined effects of temperature and moisture on humidity and their subsequent water-condensation effects when temperature falls need to be regarded in drug storage.
As soon as the herb dries (root, leaves etc), they should be immediately placed in a dry container. Handle these with great care as they can be quite brittle. Herbs with volatile oils should not be stored in ordinary plastic boxes or sacks because these materials absorb the volatile oils and evaporate them from their external surfaces. It is best to store all herbs in glazed ceramic, dark glass or metal containers with tight fitting lids and away from direct sunlight or heat.
Herbs have been provided to us on Earth by the higher powers above so as to improve our health, culinary delights and wellness. We should thus treasure their existence and respect them as an important part of nature.