Cardinal flower is a favourite of hummingbirds.

There's jewel weed in my bog and the Hummers LOVE it.

Around my natural pond I have bee balm in several colors and the hummers are all over it. Same with lobelias. The hummers arrive when the bog irises start blooming and stay to frost. Jewel weed is a favorite but it throws it seed everywhere. At least the extras pull out easy or are controled easily with a lawn mower. Never tried a floating island so I don't know how they'd do on one.
Impatients take a lot of sun when they are consistently wet. My pond is spring fed and tends to be a little cold for them.

one part sugar/3 parts water. simmer and stir for two minutes. allow to cool and put in a hummer-feeder. The best way to attract hummers

I have pickerel rush, the hummingbirds love it. Kathy

we have hummingbirds but I think they just come to the pond to drink water. We don't have anything that is really flowering yet so it can't be flowers. They just land on a plant, get a drink and then usually sit ther or in a tree for a few minutes preening and then fly off.

I have honeysuckle vine that they love. I tired the feeders with the sugar water, red food coloring and all kinds of mixtures supposed to attract hummingbirds. The only thing that it attracted was big black ants.