I happened to have 2 of the Faerie Flowerbeds (I think I got them from quests) and they drop 6 wildflowers regularly. I've also had good luck with the red trillium (and red trillium shrub I crafted in the Arboretum), white trillium, rocket larkspur, blue-flower penstemon, and talinum auranticum. They don't drop all of the time, but the drop rate is decent.
I don't have a multicolored hedge, but I believe that one drops 12 each time.