I think it would be too young. I've had best success makking cuttings on half-hard wood. You caould wait a while to make your cuttings, or perhaps someone else on forum will have advice on what you can do now. Also, cuttting off 6" from ground level should give you new shoots and perfect plants off your original pots.

Hi Brenda....I had to pot all my Salvia Leucantha as I am in Zone 5 and could not put them in the ground if I wanted them next year. Some of the new growth is pretty long already but it is growing off the branches...maybe the branches aren't dead???

Linda

Definitely not dead if anything live is growing off them. If the plant will be too leggy for you growing as it is now, cut the brown part off at about 6" from ground and more green shoots will come from it. The longer you wait to do this, the more energy the plant will expend on new shoots you don't want.