Hardy shrubs, plants and evergreens can spend the winter outside in their frost-resistant tubs but must be protected from the sun and wind so that they don't dry out.
For example, use a sun protection made of straw matting and a thick layer of mulch composed of leaves, conifer branches or spruce wood. Place tubs on pieces of polystyrene, logs or clay feet to create an insulating cushion of air between the plants and the cold ground. Position tubs close together so that they can keep each other warm. Provided the earth in the pot is not frozen, bamboo etc. should also be watered in the winter because such plants give off a lot of water on mild and sunny winter days.