Don’t be afraid to leave out your bonsai out in the garden during cold snaps, it is important to let your trees have a dormant period in winter. If the pots are shallow then you need to be more vigilant. The outside temperature in my garden hardly ever drops below -5ºc and my trees benefit from this cold period.
The whole of Europe is in the grip of a mini ice age, yet here in the UK we seem to have missed the worst of the weather. The coldest my garden has got is -3c during the day and a night -7c. yesterday we had the strange phenomena of ‘freezing rain’.
The trees that I have left out are totally covered in a thin layer of ice. The Pines, Yews, Larches and Hawthorns that I collect have endured far worse conditions when they were exposed to severe desiccating winds during very cold winters in the mountains so I am not concerned as to their wellbeing in my sheltered garden.