Most plants I bought were in large Ziploc bags or extra large plastic bags. The plant roots wrapped in very wet newspaper.
Then they were placed in a roomy and sturdy box. They last a few days that way. Good luck.

Thanks! I will give that a try.

I have found that if you wrap them up in damp newspaper and then put them in something like one of the plastic grocery bags tied loosely they will do fine. If you seal them up in ziploc bags or trash bags they tend to cook in the heat of shipment. Allowing them to have some air seems to work well.