see link

Here is a link that might be useful: link

Keep your life simple and get miracle grow potting mix or similar.

Pot them into Anderson Tree Band containers (link)
smaller seedlings use: 2 3/8 X 5 Band Pot
or just purchase 2 7/8 X 5 1/2 Band Pot as these are a bit larger and are pretty much perfect for general purpose use.

Keep them under a large tree so they receive dappled light....or an eastern exposure. When late fall arrives and it's damn cold now (and because you're in zone 5), use hay bails and compact a six inch bottom layer to rest them on and cover up to the top of the containers, only. If you use 2x10's you can create a rectangle or box and that will help keep the wind from drying out the pots and keep the pots and the hay in place. Hay is so cheap compared to other media.

Place your frame in a place where the least amount of wind is.

Dax