Maybe
@Northern Light can chime in, but given there's a fair amount of protection from the elements (except extreme cold)... I think it would be fun to have some tropicals (hardy palms etc.) here ... some tropical whimsy to counter the winter blahs.... still sorta
outside rather than encased in a suburban mall.
In the particular, the
terracotta-clad podium would be a stunning backdrop for stuff like Dwarf Palmettos which can survive extreme below zero temps and there's a couple of taller species that can survive below zero temps.
*Obviously the size of soil volumes needed would come into play with larger species.
First, let me say, palm trees are well outside of any expertise in trees I may have.
That said, I had a glance through the resources at my finger tips.
It's tough to say, I don''t know what modelled conditions for 'The Well' showed. Absent doors though, I imagine the interior condition would not be much warmer than the surrounding air. Modern lighting gives off very little heat. There's also the question of windchill.
Of larger Palm Species Windmill Palm is among the hardiest, but it's only tolerant to about -15C safely ( might handle -20C briefly) .
Given where our overnight lows can go in January/February, the recommendation would probably be to wrap the tree in burlap through the winter.
It's worth saying, as well, getting a Palm to survive a Toronto winter is plausible, but getting it to retain its leaves through winter is a different matter.
* a further challenge is that younger Palms are less hardy
Not sure you'd get what you're hoping for w/that idea.
You can introduce a fair bit of colour w/native trees/shrubs/grasses. Conifers (evergreen) ; Red Osier Dogwood, Beech Trees which hold their golden fall foliage for much of winter, Birch/Aspen for bright, white/silver bark, some bushes that retain their fruit through much of winter, Christmas Ferns etc.