Tom, here's an idea. Get some of those Moist Crystals, soak them in water. When they suck up the water, just take a hand full and stuff it inside the pot and secure the top of the pot with some waxed cordboard,, bag, tape and tie everything up and you're good to go! SOmetime I ship trees with that stuff. It works great! Just a teaspoon of those crystals expands to a lot! It expands to a cup and it weighs next to nothing on a bare root ball tree. Trust me, you will have no leaks.