I have a hypertufa planter with perennials in it. How do I overwinter it?
As the days get shorter and night time temperatures reach single digits our thoughts turn to preparing our garden and potted perennials for their winter sleep.
Overwintering success with container perennials is dependent on the ability to insulate the roots in the container from the freeze and thaw cycle we experience regularly in our winters. Plants that are grown in containers are exposed to colder temperatures (at least 2 zones colder) than those that are grown in the ground.
Hypertufa containers are generally wide shallow containers made from a mixture of cement powder, peat moss and sand. The biggest overwintering concern is keeping your trough protected from cold, drying winds.
Option 1, Bring inside: Store the perennials in their containers in a cool indoor location, eg. a wall in the garage. It has to be a cool location or the plants will not over winter properly. Move them in the late fall and give one final watering.
Option 2, Protected Location: Move the containers to a protected location outside, such as under an overhang on the eastside of the house. Group the containers close together as possible. Avoid putting the containers on raised structures such as decks because exposure to air below the surface will dry out the roots and container even faster, killing the plant and causing the trough to crack.
Here is an excellent article in Garden Making Magazine on How to Overwinter Perennials in Pots.