Pitcher plant is located to the right of the alchemy lab where the kids go when "Nature is calling!", it kind of looks like a bunch of 3 reddish tubes.
Lotus is tricker to spot, it's a vertical column of 3 purple flowers and it's to the right of the bath.
The Tiger lily is located at the top of the hill where your villagers will push the statue, it's easy to spot because it's on its own and it's orange.
Black orchid is below the Roster of the Dead, it's kind of an odd-looking plant with black petals and a green stem.
Rose plant is also easy, it's pretty much a rose bush, and it's located right by where your villagers will jump to try to get the pink jewel Door Key, to the right of the Lift.
The Golden Berries can only be found on the Magic faction, and I believe they're next to the bath as well, only on the left-hand side.
Cactus is pretty obvious, as well, it's to the right of the Alchemy lab in that little path. It...looks like a cactus, pretty similar to the Cactus in A New Home.
That's all I've got for now Oh, a potion that makes the villagers exercise and ups their Building skills is Lily + Orchid + Cactus. Usually takes about 6 uses for your villagers to gain a skill level (i.e., from Trainee to Adept), but it's easier than having them repair huts all day lol