Hardy shrubs much better planted in autumn USDA 6 and warmer.

I think fall is a great time to plant trees and shrubs in your zone. I cant tell you which time is best. I have had good luck in both fall and spring. For me it boils down to a few things - did you plant it properly, are you able to water as needed , a nice layer of mulch has been applied and some times most important for me - do they have the plant I want and is it in good condition at the nursery.

There is a set of specific reasons why autumn is preferred including the annual root growth cycle of cold climate adapted plants.

"do they have the plant I want and is it in good condition at the nursery."

Yes, this is often the overriding issue. Fall may indeed be an ideal planting time but in most areas, stock tends to be somewhat limited. Trees are usually preordered far in advance of the selling season (like NOW for early spring sales) and then harvested by the grower in winter. In many cases, once they are sold down during the season, that's it until the next year. And while many shrubs are container grown and theoretically should be available and plantable at any time, at this late date in the season, few places bring in fresh stock now (so as not to have to worry about wintering over) so again, you are pretty much limited to what they have on hand.

In addition to the issues about active root growth in fall, cooler temperatures now and typically adequate rainfall also makes establishment of fall planted stock easier and faster than if undertaken in spring, with warmer temps and drier weather looming for months on end.

fall planting.. is why many of the hardcore ... buy plants all summer long.. and at bargain time.. and HOLD THEM OVER... until fall planting time ...

and dont get confused about it being cold out there .. it might seem such to you ... but root growth can continue very late into fall ... and start much earlier than you might want to be out there in spring..

which means... the plant has two root growing seasons.. before its first experience with the heat of next summer ... and there is no downside to that ...

see link for planting guide ...

ken

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

I find my fall-planted woody plants do much better than spring; cool air temps, higher humidity, and warm soil all contribute to settling in well. Mulch well and keep an eye on soil moisture and water as needed until hard freeze.

It depends on the type of shrub. Potted stock can be planted anytime, but it may require more watering when planted during warmer months.

Evergreens, especially broad leaf evergreens like Rhodies and Laurels are best planted in Spring. Most others in early fall where you are.

Root growth in winter is comparatively minimal, plants basically hibernate in winter. Autumn is the big time for root elongation, the only time of the year when this part of the plant gets priority. Autumn in this sense is whenever the winter stem buds have formed, with some kinds under some conditions this can be as early as July or August.

We went to a nursery today in SE Michigan he told us they don't plant much after Oct 15th because there is not sufficient time to develop a good root structure before winter.

We are getting on their list for an early spring planting!

"...there is not sufficient time to develop a good root structure before winter."

It doesn't necessarily matter because they will go dormant. Root growth will continue in the spring. I have planted things during the winter (usually spring-blooming trees) and have been more successful than I would have been after dormancy.