As far as magic plants go...unless your society is very scientifically advanced, they don't know how plants work anyway. A hundred years ago we still hadn't figured out that plants take in CO2 and nitrogen to turn them into sugar. The inhabitants of your society will have no way of knowing how their food crop grows, they'll just know that it does.

The same is true for your flying plants...people aren't going to know how they float. They'll probably have learned that those plants can burn like the Hindenburg with a single fire arrow in the right place...but hey, plants burn (and a good thing too, if they're carnivorous floating monsters).

You could have all the trees be sentient plants that can separate a motile, humanoid fertilization pod for pollination...or you could just have dryads. Your characters won't know the difference.

If you create any plant, animal, or mineral with characteristics not known to our science, then you won't be able to justify them in scientific terms, unless your characters are given to explaining them in those terms.