Just before loading the trailer lightly water (don't over or under water) the plants, set them each in their own plastic bag without tying off the top of the bag but making sure the top of the bag is folded over. Place them in boxes and pad so they won't tip over in the box if needed and then mark the boxes as 'unpack first' on top and sides in red felt/sharpie pen and seal box with tape.
When actually packing the u-haul place those boxes somewhere in the center of the trailer (this will help them from becoming over heated or too cold) and also make sure they are firmly placed so they won't tip.
I've moved across the country a couple of times and each move took a week to a week and a half and all of the plants did just fine doing this. They'll be okay without light for that long and the plastic will help keep them from drying out. Be sure to unload and unpack them as soon as you arrive at your final destination.
One more tip. Some states have outdated laws on the books about transport of plants accross state lines. So, as the professional movers I hired told me, "just be quiet".
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