Question: I have a two-tier retaining wall. On the first tier I want to put 6 or 7 giant plastic pots. In these pots I was thinking of planting some rose trees or a small evergreen with flowers planted around it. My concern is about the trees or evergreens that I plant, could they survive the winter in the pots? If not, what do you suggest to winter them. I know once they are planted, the pots will be too heavy to move. Will there be damage to the roots, or can the roots freeze?

Answer: Your idea for gardening on the wall sounds good, but trying to winter-over container plants is risky. Even plants hardy in your region are subject to root damage. Also, plastic pots may suffer frost cracks if the soil inside expands as it freezes. If you must leave the containers in place, I suggest using wooden ones. Alternately, you could plant separate pots of flowers within your larger planters, and remove the small pots for the winter. Sink the pots of perennials right into the ground and winterize them as you would in-ground perennials. You can also contact the ornamentals specialist at your local extension service and see what they suggest for folks in your area. Good Luck!