Karl Forester is a cool season grower and as such is ok with fall transplant.

Using a root stimulator can only help, I use it with almost everything I plant. FYI: Have had problems with planting Miscanthus 'Morning Light' in the fall.

As warm season growers Miscanthus are expending their maximum energy in the fall in flowering. Transplanting at that point seems a risky business when mid-late spring or even early summer planting guarantees good results.

When transplanting any grasses I always slice the root wad along its length once or twice to facilitate faster and better root penetration into the surrounding soil and typically add a shovel or two of fine chipped gravel to the soil. I've never used root stimulator -- probably never will on a grass. They always seem to do well so far.

I've found that soaking the root ball and rinsing the soil off with a hose prior to transplanting works well to loosen the roots to stimulate their growth. If the root ball seems a bit dry (as is often the case with plants I buy as I get them on clearance) I soak it for a few minutes in a bucket. I've found there's less transplant shock than with slicing the roots and actually has the same effect.

good suggestion -- I'm such a brute.

All Miscanthus are warm season grasses so I agree that your Morning Light would have most likely had problems being planted/transplanted/divided in the fall.
And yes Karl is a cool season one so any cool weather is when their roots are actively growing so now is a good time for Karl Foerster.

Actually while rinsing off the roots does lessen the 'transplanting' shock at anytime of the year, the slicing is desireable to rid the rootball of any severe boundness for those taken from a container. If the circling entwined bound roots are not removed then the grass will not thrive in its new home. It also is the best way to stimulate new root growth. I usually slice off the bottom 1/4th of the rootball and then score it up the sides a few times.
If the grass is not pot rootbound then the rinsing would be alright to loosen the roots.

Sue
"The one thing all gardeners share in common is a belief in tomorrow"

LOL, Is it to late to plant Miscanthus already? Is there a date you could suggest it be planted by? Of course every year can be different, but I would like to know what you think as we are in the same area.