It can be done, but if you transplant them this fall, you may not get to enjoy the blooms this fall.

I would mark them and transplant them in spring.
Or since you seem to have more than one plant, transplant some this fall, some in spring.

I actually prefer to transplant late blooming perennials in spring, early bloomers such as Bleeding Heart in fall.

Yeah, Aster novae-angliae usually have long ugly legs. You can keep them from getting leggy by pruning them in spring.
I normally cut my Asters down a few times until July 1.
This year, rabbits to the job for me, especially for Aster novi-belgii......too much actually. Bummer. They don't touch my Aster oblongifolius, though.

Thanks Mone! :)

Btw, I have harvested larkspur today. I'll send it to you soon! :)

I grew both 'Purple Dome' and 'Alma Pötschke' New England asters, but hated the way the plants looked. By the time they bloomed in the late summer/fall, they looked like blue-flowered/pink-flowered mini-palm trees.

Sure did love the flowers, tho.

PV

Yeah, I love the flowers too. However, I really need to transplant it because it's tall. My plants aren't all organized properly. :)

This is a notorious problem with Aster novae-angliae. I've winter-sown it (got one pretty pink plant) and have several cultivars and they all seem to get something of brown raggedy legs, although Alma Potchke seems to be a bit better. This summer is hot and dry and the problem seems worse. You can always put them in the back of the border and plant stuff in front to hide the foliage.

I gave all the asters a haircut in late May this year, to make them shorter and bushier, and hopefully less floppy.