A weed is a plant growing somewhere someone doesn't want it to. Common examples of "weeds" are dandelions and stinging nettles. These two examples are particularly ironic, though there are many others.
Considering dandelion first, Taraxacum officinale is a liver tonic and diuretic, also a source of latex for rubber, high in potassium and provitamin A and various other things. It's notably similar in a appearance to the related Lactuca virosa, lettuce, and under the soil bears a resemblance to Jerusalem artichokes, to which it's also related. I have eaten roast dandelion roots and because of their inulin content they taste similar to artichokes. They also propagate very easily due to the windblown seeds and the fragility of their roots, each of which can produce a new plant when broken. Some herbalists put dandelion root in every prescription.
"TaraxacumOfficinaleSeed" by Greg Hume - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:TaraxacumOfficinaleSeed.JPG#mediaviewer/File:TaraxacumOfficinaleSeed.JPG
"Ragwort and caterpillars, Croucheston - geograph.org.uk - 1388879" by Trish Steel. Licensed under CC BY-SA 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Ragwort_and_caterpillars,_Croucheston_-_geograph.org.uk_-_1388879.jpg#mediaviewer/File:Ragwort_and_caterpillars,_Croucheston_-_geograph.org.uk_-_1388879.jpg
The question of use and value to human beings is an issue here too. Just because one species is in a place which another finds inconvenient, such as a ragwort plant and a human, doesn't render it a universal problem. The reason I bring this up is not to be awkward but to point out that the way we perceive organisms is clearly influenced by our own reactions to them, perhaps as a species. Zingiberis officinalis or ginger, for example, we perceive as "hot", but in fact spicy plants are merely ones which do things like stimulate human pain receptors or increase local circulation. They presumably don't do the same thing for, say, an insect which is eating the rhizome or for that matter a mould growing on it. Nor does this simply apply to taste, but to every aspect of reality.
That leads us to a rather cold, impersonal world which is however kind of vegan in its outlook, since we have no more right to occupy a position than a germ has to kill us or a weed has to grow there, and of course no less. It's a world in which there are coordinates but no origin, measured in "objective" terms, but also a world in which there is paradoxically no care. There is another world, and it can be equally vegan.
As I'm sitting here typing, I'm only minimally aware of my glasses making the text in front of me easier to see clearly. I'm also only minimally aware of the positions of the keys on the keyboard. I'm more aware that my fingers are cold and that my hair is hanging down over my eyes. A physical description of what's going on would not take into account those levels of awareness. Now, suppose the E ky wr to stop working. I would thn bcom vry awar of that fact, and th ky in qustion would becom an objct of my consciousnss, and possibly also of yours. It would move from being an assumed functioning part of my world to an obstacle to my communication. Similarly, the facts that my hair is hanging down and my fingers are cold makes them things I care about. This is an entirely different world, and in a sense it's a world with a centre - myself - and distance, at least metaphorically. In a sense, numb hands are further away than hands which feel normal. There's a sense of reaching for them to make them do what you want. Things which become problematic obstacles are things you care about.
Ginger as a spice is often in a world I care about, particularly as my favourite smells are ginger and coffee. If, however, I post a picture like this:
which is the structural formula for shogaol, one of the "spicy" substances in ginger, and of course a representation of a reality which is quite different. It probably doesn't shout "spicy" at you although it does to me because of that side chain with the oxygen on it. It also creates an impression of the flavour and odour of ginger in my experience right now.
Applying this to herbalism, herbalism ought to be medicine in the realm of care rather than the realm of the cold and impersonal. It's about weeding, possibly using the weeds but also respecting them for their meaning and use to other species as well as in their own right. It's also about veganism of course, to me at least, and as such is about compassion. The mainstream medicine in this country is not herbal or vegan of course, but often does involve compassion although it's difficult sometimes to show that for practical reasons, often money-related.
Possibly then, the real division in medicine isn't between orthodox and alternative at all, but between caring and not caring, and both can occur in both contexts. Patients need to matter to the people to whom they come in contact in the same way as herbs and bacteria need to matter to people. It's also possible that orthodox medication could matter just as much to someone in a particular predicament, because it provides their answer, and this could be a completely orthodox antibiotic or painkiller.