Can Hypertufa Survive Outside Over Winter?
(Information provided by Hypertufa Forum contributor GardenChicken:)
Here in Calgary the average winter temperatures are generally several degrees below freezing. We have regular freeze/thaw cycles throughout winter and occasionally week-long cold snaps as cold as 40°F. When a Chinook rolls in our temperature has been known to rise 54°F in as little as four hours. This causes a great deal of melting snow, which promptly becomes ice when the temperature plummets a few hours later.
I have two troughs that remain outside comletely full of soil. The older trough is aout 9" x 18" x 7". The walls are just over 1" thick. It was made using fibreglass fibres, perlite, peat and cement. The second trough is 20" x 30" x 13", with 1 ½" thick walls. It was made using perlite, peat and cement. This one has chicken wire in the walls. Both have drainage holes.
My hypertufa is left outside year-round and there has never been a problem with cracking or breaking. It gets no special treatment, no cozy cover-ups, and none of it has ever been sealed in any way. It seems to make no difference what recipe is used, or if it has been reinforced.
Once properly cured, hypertufa really is freeze/thaw-proof.