Variation in plant properties?
This is a newbie question, and may head too far into the woods in more ways than one, but....
I am just getting serious about learning herbal medicine, though I have been making natural dyes from plants for the yarn I spin and the fabric I weave for most of my adult life. One thing I have learned is that the same plant grown in different places can have quite different properties. For example, the pokeberries that grow in dry, poor soil on the east end of my farm give bluish-purple hues, while those grown in the richer, damper soil on the north side give pinkish-red colors. The wild bidens from around the pond give bright yellows, while those growing in the yard give intense oranges. There was a hedge of five privet bushes at a house I rented years ago before I found my farm. Four of the bushes gave the usual privet colors-boring yellows and olive drabs-- but the one on the end--though it seemed to be exactly like the others-- gave an intense spring green. Cuttings from this plant when rooted and grown in other locations just gave the usual privet colors, so I figure this particular plant must have had its roots down into a pocket of some mineral to give it this property.
So how serious is--and how do you deal with-- this kind of variability in the medicinal properties of herbs? On one hand, plants of the same type must all have the same general properties, or the books and other guides we use wouldn't work. On the other hand, the differences between purple and red, yellow and orange etc. matter to me, and comparable differences in medical properties matter even more. Is there a way to learn the variables in a given plant species, other than years of experience working with the plants in a particular location?