I do my Fall planting and transplanting of perennials, shrubs and trees between Mid August and Labor Day. Bulbs I plant from Mid August thru Halloween. This time frame seems to allow for the roots to get established before winter sets in.

I have bad luck with fall planted plants. They seem to need a longer period to develop roots, and end up heaving out of the ground during early spring freeze-thaw cycles. I think the "fall planting" idea is perpetrated on us to sell more plants. They usually die on me in our climate.

I'd start moving plants now, cutting the leaves and flowers back and shading the plants with boards and watering every single day. Better yet, clear the spaces in the cool of autumn and wait till spring to transplant, when you won't lose any plants at all.

When the Maximillan Sunflowers bloom and the Joe-Pye Weed is dark mauve.
That was the sign last year.
This year is so unpredictable with the higher than normal temperatures.
I've put in and moved around some perennials for next year this month so they can get some roots established before the cold.
I'll wait until October for the bulbs.

I don't transplant anthing during the heat of summer, An exception is my agastaches. Those need a 4 month period to get restablished so those are moved transplanted or planted out no later than early August, I will wait until the temps go down a bit more during the day to do any other fall planting. Mid 70's seems to work well for me as long as it isn't too late in the season.

penny

I try to move stuff in September and then just keep working cleaning up etc til the snow flies...Fall lasts for me until the first snow.