Dug one which was at least that size 2 years ago. Removed all unwanted material. After getting it home, I timmed all roots to 4 inches. Put it in a tub. And sold it within 4 months as I could not move it alone, nor keep it watered during the day. That stuff is like a weed. Will pop buds & explode as soon as it realizes there is water. I did not face any die-back. Digging was done late winter.