From the top of my head, missing quite a few, and not counting Bloomed forms, which are simply irrelevant for now on Nutaku:

Counter Attack
Hypericum: Gold, Event
Mirabilis: Gold, Event
Rose: Gold, Gacha
Anemone: Rainbow, Gacha
Helenium: Rainbow, Gacha

Skill Activation:
Geranium, 1.2: Gold, Event
Justica, 1.2: Gold, Gacha
Apple, 1.2: Gold, Gacha
Cyrtanthus, 1.2: Gold, Gacha
Laurentia, 1.2: Gold, Gacha
Cymbidium, 2x first turn: Gold, Gacha (she seems to be the only one with first turn activation actually affecting the whole squad? )

And then there are a bunch more girls with 3rd round activation for the whole squad (like Moonvine & Tachibana from Event) or 1st turn activation only for themselves (like Dendrobium and Cactace Bride). These are great units when starting your first trigger squad, but the ones I listed above are simply better alternatives. Especially Cymbidium is one you'd REALLY want on a trigger team.

Oh, and I just found the girls are listed here as well, ordered by ability, also telling whether it comes pre or post evolved:
http://harem-battle.club/wiki/Flower.../FKG:Abilities