Medicinal Herbs Should Only Be Used in Season?
Answered by: Conrad Richter
Question from: Christine
Posted on: August 09, 2004

I have been told that medicinal herbs should only be used in ‘their season’ for optimum use... thereby moving on to another herb in its season, so as the body will not over absorb a certain herb and render it useless.

I was wondering if you have a chart of herbs and their seasons or can recommend a booklet which would show me this.

There is some truth to a seasonality of herbs, but it is not quite as you think. Most herbs accumulate medicinally active compounds at different stages in their lifecycle. For example, most aromatic herbs produce their most potent leaves just as the plants are beginning to flower. However, some medicinal herbs produce most of their medicinal compounds in the first year and not in subsequent years while others produce little in the first year but produce more in later years. Feverfew is an example of a herb that is more potent in its first year; echinacea and valerian are more potent in later years. The plant part used is important too: roots generally reach their greatest potency in fall after the plant has begun the process of dying back and shutting down for the winter.

Part of what you are referring to is the phenomenom that some medicines, including herbs, may only be effective for a while and then gradually their effectiveness diminishes. This phenomenom occurs not because the medicines themselves diminish in potency; it’s because the body naturally becomes less responsive to the medicines over time. Well known examples are narcotics like morphine which patients must take in increasing doses in order to achieve the same painkilling effect. Echinacea is another example: as a cold preventative herbalists will recommend taking it a few weeks at a time, with a week or two break in between.

With some medicines, including some herbs, undesired side effects can develop if they are taken for too long. For example, ginseng taken for months at a time will have the opposite effect of what was intended: instead of boosting energy and combatting stress, the body eventually becomes more exhausted and less able to cope with stress. Ginseng is best taken for a month or two and then stopped for while before resuming.

Ginseng is an interesting example because there are two main forms that are taken. One, the asiatic (also known as chinese or korean ginseng) is sometimes prescribed in the winter months because it is generally a ‘warming’ herb according to the traditional Chinese classification. The other, american ginseng, is sometimes prescribed in the summer because it is considered a ‘cooling’ herb. (This is highly simplistic: the differences in usage of the two ginsengs is much more complicated than that.)

An important point to realize is that these effects are generally only a concern when the same herbs are taken for long periods. If the illness is a chronic one, it is often a good idea to change to a different herbal remedy after a while. A professional herbalist or naturopath can advise if and when this is necessary. It is very difficult to encapsulate all of the complexities of these effects into a chart as you were hoping for. And I am unaware of a book that deals with this topic comprehensively. Herbalists learn about these effects partly from training and largely from experience.

I have a dog from a rescue society and I am trying to build up his immune system because of on-going skin problems. Nettle and Dandelion have helped, but I don’t know which season I am in now!! I see lots of Red Clover around... perhaps this would help?

You should have a look at two books we carry on herbal dog care. See:

1. The Complete Herbal Handbook for the Dog and Cat

2. Herbal Dog Care

Both will help you to understand how herbs work and how they can be used to support your animal and bring him or her back to good health.

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