Potted specimen stuck in during summer will not immediately have same sun tolerance as when it is fully established. Also if it was in a shaded environment at the production facility its current set of leaves is not sun adapted.

cut off the flowers so you dont have to look at them ...

then water properly thru fall ..

a common folding lawn chair would have been much simpler .. in case this one takes flight.. lol ... [though your set up is pretty ingenius.. two dirty thimbs up ...]

surprised the hosta are thriving in that sun ... undulata albomarginata or its ilk .... if you care ....

you arent a real gardener until you have 100 pots to plant in fall ... just because you get your hands on something.. doesnt mean its time to plant it .. especially july and august for most of us ...

WTHeck is lobster compost.. thats a new one on me... got a link ...

ken

ps: i prefer not to amend planting holes.. but looking at the rest of the stuff.. you know how to do it in your yard .... [and.. no cost on amending.. means more money for plants.. which means more pots to plant in fall ... full circle.. bazinga .. lol ..]

pps: how does emily make man shade??? ... probably spellchuckerupper ....

My experience with some of these more sun tolerant macs in northern latitudes is IF you have moisture retentive soil and some added irrigation when needed they do ok. In fact, on these reblooming types the more sun you give them the better. Here in MN I have sandy soil so I keep them out of midday sun and they do fine requiring less frequent irritation. Year one on a mac is about establishment, don't worry about the flowers browning out. Not much you can do.

Thank you, everyone! Yes @embothrium, I definitely think it is a bit in “shock” - this is our first real heatwave since I planted it. Temps in Boston at a record high for June this year! @ken - I have NO idea how that hosta does so well there, ha! Behind it, you will see some bearded irises, which of course bloomed about a month ago, but they are pretty happy there as well. That side of the bed, against the shed, is “shadier” but it is still certainly a sunny spot. You’re spot on about more money for plants - the lobster compost is pricey! @pennlake, thanks for the perspective. I’ll keep reminding myself that it just year 1.

If I was planting it so close to the summer months, I would water the soil -never the leaves- every time that the top 4" dried out: start watering the soil at the crown/base and then continue watering outwards in all directions. Then provide 2-4" of organic mulch, protect from drying summer winds and give it extra shade (like you already have). I do not know if Bloomstruck can really tolerate "extra" sun (not on year one) or if the garden center was trying to make a sale; however, you are very close to locations where some macrophyllas can tolerate unusual sun exposures. My MIL, for example, had Nikko Blue growing on the west side of her home. That would never happen in my home (Texas).

The plant has a limited root system at this time so expect leaf/bloom/stem wilting during days when temperatures reach or exceed 85°F. But if the soil is moist enough, they should perk up on their own in the morning (if not, the soil was not moist enough so water them right away). In an extreme wilting event, you can either water immediately or you can extract the plant from the ground and dump it in a pail full of water until it stops throwing air bubbles. Then replant it. That should re-wet the rootball when it becomes hydrophobic and begins to repel water even when the soil is wet. The extra shade should help minimize the problem but it always sensitive to this in year one.