While many people may think that taste and flavor are the same, they are actually different. Here’s why:
Taste refers to the senses in the mouth and has to do with how the tongue and mouth interact with food and drink. The tongue has two types of receptors: one is for taste, determined by your tastebuds found all over the tongue, while the other is for "mouthfeel," or the free nerve endings located throughout the inside of the mouth and all over the tongue. There are five tastes: acrid, sweet, bitter, sour, and salty, although Ayurvedic medicine calls "astringent" a taste and now some chefs include "umami" (a Japanese word meaning "delicious"), a new taste described as meaty, savory, and earthy.
Flavor, on the other hand, is a combination of sensory stimuli that includes taste (gustatory) along with smell (olfactory), touch (tactile), and temperature (thermal). For example, spicy is not just a taste, but can also be painful.
In terms of herbs, taste is the sensorial effect on the mouth and tongue while flavor represents how an herb works. For instance, ginseng is acrid and sweet in flavor but not in taste (ginseng sweet is hardly what most people think of as sweet, like blueberry pie sweet!). But there are other meanings and influences of tastes and flavors. Basing an herb’s properties on flavors was a way that herbalists identified what today are biochemical constituents. For example, alkaloids are generally bitter while glycosides are typically sweet.
The major breakthrough in my book, Planetary Herbology, was learning that flavors (or what was called tastes back at the time I was writing the book) was not only denoting a flavor but also an action. For instance, echinacea could be described as having a strong spicy taste but because it stimulates the immune system by summoning white blood cells, it could be described as having a bitter flavor. This further complicates the situation so that both flavors/tastes and actions/uses need be considered together and perhaps occasionally with recognition of an herb’s major biochemical constituents (for instance, berberine is always bitter and detoxifying).
Even more, the actions of flavors according to whatever energetic system is used also need to be considered. For instance, the Chinese Five Phases defines flavors according to the elements involved, as do the Ayurvedic humor classifications. These are ancient cosmological systems that represent the whole of nature and suggest that everything contains all tastes and flavors. Taken by itself, this can be confusing and limiting. For instance, while Ayurveda describes "astringent" as a flavor, TCM does not. Some have tried to equate the flavor sour with astringent but both flavors have different chemistries and actions. On the other hand, cinnamon is an astringent used for diarrhea in Central America and yet it is not specified as such in the TCM materia medica where it’s categorized as an herb that stimulates metabolism and circulation, which is not an astringent-type action.
As another example, tinospora is considered to have a cold energy and bitter flavor in Traditional Chinese Medicine (TCM) while Ayurveda states tinospora (guduchi) has a warm energy and bitter and astringent flavor with a post digestive effect of sweet. The difference in the TCM and Chinese use of the same herb is that Ayurveda recognizes tinaspora as having a tonic effect as well as being a detoxifying herb.
Herbalism is different today than ancient times and yet herbal theories need to continue evolving. I imagine that flavors and energies will have an ongoing usefulness in understanding clinical applications and bio-chemical constituents. It is the flavor and its actions, however, that are of primary when considering the use of an herb.
 (On another note, I don’t think echinacea actually detoxifies like an herb containing berberine, which stimulates liver function to detoxify the body, but instead has a detoxifying effect through neutralizing the hyaluronadase enzyme, which blocks the germ growth process that develops infections.)