Mallow Family Demulcents.
Here come the YAMFDs!
A demulcent is a plant (or plant part) which contains enough mucilage to soothe mucous membranes.
And most (if not all) plants in the mallow family (Malvaceae) contain loads of mucilage.
I've half a dozen species of mallows in my garden (if they come up ... I moved my garden last fall, and things aren't certain yet), and I use the aboveground parts of all of them. They're similar enough to end up in the same jar.
That's musk mallow (Malva moschata), rose mallow (Malva alcea), hollyhock (Alcea rosea), marshmallow (Althaea officinalis), garden tree-mallow (Lavatera thuringiaca), and I'm sure I've forgotten one or the other of them.
If you're south of me you probably have one or the other wild mallow (Malva sp.) - use the lot, they're all the same.
In the SW US you'll find globe mallows (Sphaeralcea sp.), poppymallows (Callirhoe sp.), and the little creeping Malva neglecta (among others) - use them all. (Globe mallows are hairy enough to warrant coffee filters, in teas.)
If you're in a subtropical or tropical climate you probably have loads of hibiscuses - use the lot. Of course, the roselle (Hibiscus sabdariffa) is sour sour sour, but underneath that is - mucilage.
The usual part used is the root, but there are no wild mallows in Finland (or if there are, they're in the southwest corner, and rare enough to leave them alone). So I grow my own mallows. And I don't use the root, cos if I did I'd have no more mallows.
No, I pick the leaf, and sometimes the flowering tops, and dry those for tea.
I use them for their soothing action on the stomach, the gut, and the urinary tract. Mallows also give body to ordinary herbal tea blends.
Nice plants, are mallows.