i cut nothing to the ground.. literally ...

leave 3 inches or so.. and you know where everything is in spring ...

within the next week .. in MI ... will work ... after that.. its getting a bit late... but... if ...

insure you take a big enough gob of soil.. so it doesnt heave out in spring thaw ... then you should still be OK ....

or delay to soil thaw in spring.. and do it as soon as the soil is dig-able ...

ballon flowers were never long lived when i was in livonia... i might leave it for spring moving.. at least then.. if it dies.. it was winter.. and not you ... lol ...

again.. do not cut all the way to the ground ...

ken

that info is NOT plant specific ... it helps to know what you are talking about... but in most cases.. its not imperative ...

we had a real hard frost out here in adrian .... which means.. the soil is going to start getting cold...

we usually like to move things in about sept or so.. so we might get some root growth ... before the soil gets to cold ...

if you move now.. most likely.. they will just sit there ... which is OK.. if they dont pop out of the ground in late winter.. as the snow melts... hence the big gob of soil ...

ken

A confusing range of heights are given on-line for Phlox paniculata 'Laura'. As said, a contributory factor may be P. paniculata 'Little Laura'.

Here, balloon flower can be quite long lived compared with many perennials. As you say, it doesn't favour being moved, though I've certainly had to move them (usually successfully). If your one was only planted this or last year, I wouldn't hesitate to move it if needed.

Obviously, informed perennial gardeners don't all have the same growing conditions, tastes in plants, styles of gardening, time available, etc..

That said, I've always cut herbaceous perennials down to ground level by the end of fall. For me, I'd say maintaining close perennial plantings puts a premium on garden hygiene. The point about difficulty in identifying individual (summer and fall) plants in spring is well taken.

Certainly do agree re avoiding winter heaving. More generally, the biggest thing here when planting, is not leaving the plant encased in the peat-perlite mixture they're typically grown in (viz. differential rates of freezing).

My feeling is that next year your Laura will grow taller. With few exceptions, the first season in the ground does not give a good idea of what the plant will actually look like once established. Generally, commercial tags that are in the pots at the nursery are supposed to give you an idea of height and width in the 3rd season of growth.

As to the Balloon Flower, I highly recommend waiting until spring. Right now it is in the process of going dormant. Any root damage it sustains in the move will not have time to heal before the ground freezes, and the result will be a stressed plant. Moving it when it first appears in the spring, when it is ramping up for a growing season and is full of vim & vigor gives you the best chance for survival.