Tea is made from the plant Camellia sinensis using fresh or treated leaves. Rarely another species from the same genus may also be used. And that's it. Anything made from flowers, herbs berries etc is an infusion, also called a tisane. Once tisanes were made using barley water, but this meaning has more or less died out, although you may be able to get barley water in squash form in shops.
Tee wird nur aus den frischen oder behandelten Blättern der Pflanzen aus der Camellia -Genus hergestellt. Hauptsächlich Camellia sinensis. Alles sonst is kein Tee. Auch wenn so genannt.