Ginseng is abnormally rare compared to other plants. Fanny Blossom, Fatfern, and Whisperwood are much more common. Black Roses seemed pretty numerous as well.
Oak Tears seems somewhat common (especially in planters in buildings), but are useless, since no recipe in the game uses them. Holy Basil a bit rarer (and only useful if you choose Allan).
Dragon Nail I found a couple of, I think, but it was pretty rare. Moonshine I can't recall EVER finding. Stardust was pretty rare, with only a few on Sentinel Island. Fahrangite was pretty common in Sentinel Island and in some places in the Fjords, but was almost non-existent in the Valley.