Posted: 22/04/2013 at 18:26
I do get serious frosts down and -25C is not unsuual in recent winters. +38C happens for at least a week most summers.
All my pots for show are either thick, frost proof ceramic or terracotta look plastic. Real terracotta isn't frost proof enough and flakes. It also absorbs too much moisture in summer and can leave roots dry. To save on weight and give some winter insulation, I use corks as ballast and crocks in the bottom. They allow drainage but also absorb some water so roots don't dry out too quickly. Works for my hostas, lillies, shrubs, herbs, dahlias, acers and veggies.