We started harvesting our arnica blossoms earlier this month. I've now got a batch slowly extracting in light, non-greasy fractionated coconut oil. Expect to have arnica salve sticks by the end of this month!
The arnica we have growing in a permaculture patch here is a. chamissonis, a native North American species that's medicinally equivalent to the European alpine arnica montana. Arnica chamissonis grows better here in southern Appalachia, so that's what we use.
I started our arnica patch last year, and it's now well established and looking good.
Extracts from arnica flowers are used topically to help heal bruises and muscle strains or sprains. Arnica should not be swallowed or used on broken skin.