A hot infusion is the method most people are familiar with and involves pouring boiling water over your herbs and allowing them to sit a certain period of time. This method is best used for the delicate “aerial” parts of plants such as flowers and leaves.
This method uses cold water overnight to extract the compounds desired from the herb. With some herbs, hot water will not extract the desired constituents, extract undesired constituents, or could destroy the medicinal properties of the plant. There are no common properties of herbs from appearance alone that would allow you to determine if hot or cold infusion is best. A naturopath or herbalist should be able to tell you if a cold infusion works best for a certain plant. Some of the more common herbs where cold infusions work well or are necessary are listed below:
The 3 water extractions above are the most common ways to prepare a medicinal tea.
Dr. Cheatum and Dr. Doize are Naturopathic doctors writing about health topics from a holistic viewpoint.