There's a problem with planting evergreens in containers here in Zone 5... Our winters are just too harsh. Plants in containers aren't as well insulated from the freezing temperatures as those in the ground, so perennial or hardy plants often won't survive the winter in containers. Evergreens are also vulnerable because once the pot freezes the roots are unable to take up moisture while the foliage continues to transpire in the dry winter wind. Some gardeners succeed by pulling containers into an unheated garage for shelter during the coldest months. Thats a great way to keep pots planted with spring bulbs like Tulip or Hyacinth.