QuestionsHow to growTrees and ShrubsChoosing trees and shrubsPruning of trees 0 Vote Up Vote Down Mairead Caulfield asked 7 years ago I would really appreciate it if you could tell me when is the best time to prune the trees in the photo and if you could tell me what species of tree they are? 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 4 years ago The trees are Thuja ‘Smaragd’. It is a conifer and makes a small columnar tree. If you want to keep them to a smaller size, you can clip lightly in April. But try not to make them looked too trim.