Bees and Butterflies are both open to going fairly high.
Bees are raised on the 14th floor roof top of the Royal York.
Butterflies reside in the mountains in parts of Mexico.
That said, they would prefer not to deal w/high winds.
That can be more of an issue on higher floors.
It can be mitigated some by using a trellis or screen though one needs to be sure one isn't blocking the sun in so doing.
Better still, if one has the room, growing a thick native shrub that can mitigate the wind can work too.
In terms of attractiveness to bees, I've never seen them love a plant more than Wild Bergamot.
Walking past a patch with which I am very familiar last summer, I lost count of the bees (hundreds).
*** you are right to note that using a variety of plants is good, but you also need a critical mass of any one. It helps the plants survival but also makes it more visible to insects from a distance.
The question does then arise of how much planting room there is on a given balcony.
I can supply a much longer plant list; but figured those were a good place to start.
Additional resources here:
Planting as many of these plants in your garden will sustain butterflies by providing food year round to all the stages of butterflies. Some non-native plants, while excellent nectar sources do not feed the caterpillars that grow into butterflies, where as many native plants serve as nectar and...
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