Anyone happen to know what this is? It didn't have a label when initially purchased a few months ago. At the time, it had no blooms and was just a nice cluster of small leaves.

I went away for a few weeks and just got back, and found it suddenly exploded into many beautiful purple blooms! An unexpected but pleasant surprise. The temperature recently dropped quite a bit (near freezing), which must have triggered it. Any thoughts? I'd love to find out the name to hopefully find a few more of them. Each bloom is roughly 1 inch in diameter.

Aster I believes, could be New England Aster (Symphyotrichum Novaeangliae) or New York aster (Symphyotrichum novi-belgii). There are many cultivar of both

I lean to New England asters.
New England asters tends to be taller, bushier, thick stems and hairy leaves
New York asters tend to be shorter, thin stems and smooth leaves.

Macrocentra said:
I went away for a few weeks and just got back, and found it suddenly exploded into many beautiful purple blooms! An unexpected but pleasant surprise. The temperature recently dropped quite a bit (near freezing), which must have triggered it.

Someone correct me if I'm wrong but for fall flowering asters I think it is more likely daylength (which is really a misnomer since plants really measure the length of daily darkness) that initiates flowering rather than temperature.

I think that is correct actually, yes. I mainly just meant the general seasonal transition.

Thank you! I was wondering if it was maybe an Aster. It's so much larger and bushier than I've ever personally seen Asters though, so I wasn't sure.