Wait until you are packing up. Cut the plant down to that size in the pic, or a little smaller, dig up a decent sized clump of roots (no more than 5-7 gallons in volume) and shake some of the soil out of them. Water once more. Place the root ball in a kitchen trashbag lined with wet newspapers and sinch loosely around the crown. If you've a bunch, you can stack a few a in ventilated plastic storage tub. Or just sit the bags on the floor of the mover. Lucky for mopheads, they transport fairly well. If kept in SHADE, they can live for quite a while in this fashion. On a side note, I've had a barberry and a burning bush stashed in black trashbags for two years and they haven't even needed water, and even survived temps down to -15.