My knowlege of Melianthus is that it's the nectar that is used and no other part of the plant. That's where it gets the name honey bush.

There is one growing happily behind the botany dept. building at UF in Gainesville. I am going to try it this year. I live about 15 miles south

New Zealand Flax? Yes, I overwintered it by treating it as a houseplant in a low humidity 65 degree room next to a west facing window with medium light. It came through fine.

This isn't about h-birds, and it's more about buzzers than hummers, but it seems like a reasonable follow up anyway. There's a narrow path along one of my borders, between a mixed bed and a small pool - about 25' long and only 3' wide (the path; the mixed bed is about 10' deep) and for over a month now the racket from the mixed bed has been astounding. This border is backed by old spruce trees and has a long row of evergreen euonymous (not one of the invasives, this is 'Manhattan' or a similar large-leaved variety) between the trees and a row of tree peonies, mountain laurel and azaleas, underplanted with gingers, geraniums, and various other perennials. Closer inspection revealed that the racket was coming from the euonymous, which has been blooming for weeks. After an even closer look, I realized that the buzzers were not bees at all, but flies. I can't detect any odor from these flowers, but there must be one, and it must not be anything that would appeal to people. Are there other plants that attract flies by the millions? These bugs (or are they insects?) don't seem to congregate anywhere else in the yard, and don't seem to be doing any harm. And, they don't scare anyone the way the bees that are swarming the clethra do.