I am a new gardener and I've recently built two brick planters that hold approximately 1/2 - 3/4 yards of soil. The planters sit up against the south side of my house and get half sun, half shade.

I made the initial mistake of planting quickfire hydrangeas there (I've since learned that they will almost certainly die). I am wondering if there are any plants that can survive a 5b winter in these planters. Also, would it make any difference if the planters are insulated with, for example, Styrofoam?

Any guidance is greatly appreciated.