I have recently started studying herbs and I understand they are categorized on a scale from hot to cold. I know that some herbs can move in different directions and it appears some can be warming and cooling both depending on how they are used. Is it true that a single herb can be both warming (stimulating) and cooling (relaxing/sedative)? Thank you for your time .
The study of Chinese herbal medicine generally and particularly with formula creation is complicated to say the least. There are certainly herbal ingredients that will alter their nature depending on the overall function of the formula, but limiting these views to a simple paradigm of stimulation vs. sedating is only touching the surface.
Our site has an extensive but ultimately small presentation of herbal medicines in the Chinese system. If you start in the individual herb database section and the formula database section you will see how they are categorized. Going through those categorizations will give you an idea of the breadth and depth of Chinese herbalism. For example view individual herbs for their functional categorizations, or formulas by their tcm diagnostic categorization.