Black Hills Spruce
Colorado Blue Spruce
How To Prune Evergreen Trees
How and when is the best time to prune (trim) evergreen trees?
The best time varies, depending on which type of evergreen (conifer) tree that you want to trim.
Spruce trees and fir trees do not grow continuously, but can be pruned any time because they have lateral (side) buds that will sprout if the terminal (tip) buds are removed. It's probably best to prune them in late winter, before new growth begins. Some spring pruning, however, is not harmful.
To prune spruce trees and fir trees, snip off about half of the tip on new bud growth. Removing half of the new bud growth will cause the tree to not grow at that point until the following year while the remainder of the tree continues to grow. With this practice, you can actually shape or train the tree shape and cause the tree to become more dense.
If you want the all natural spruce tree look as found in a forest, never prune. If you want maximum privacy or a particular shape, then prune each year while the tree is young.
Pine trees only put on a single flush of tip growth each spring and then stop growing. Prune pine trees in late spring before these "candles" of new needles become mature. Pine trees do not have lateral buds, so completely removing terminal buds will take away new growing points for that branch. Eventually, this will leave dead stubs and the main reason why shearing pine trees is never a good idea.
Pine trees seldom need pruning, but if you want to promote more dense growth, remove up to two-thirds of the length of newly expanded candles. Do not prune further back than the current year's growth. With this practice, you can actually shape or train the tree shape and cause the tree to become more dense.
If you want the all natural pine tree look as found in a forest, never prune. If you want maximum privacy or a particular shape, then prune each year while the tree is young.
Note: For a more compact evergreen tree, prune the leader as you would prune the new lateral growth while the tree is young.
This will result in a shorter, more dense, compact tree. Correct pruning does not harm the tree whatsoever, actually pruning sends a message to the tree to encourage more growth to the branch affected by the pruning.
Arborvitae, junipers, yews, and hemlocks grow continuously throughout the growing season. They can be pruned any time through the middle of summer. Even though these plants will tolerate heavy shearing, their natural form is usually most desirable, so prune only to correct growth defects.
Note: Fallen needles are a good source of nutrients (natural fertilizer) for any plant or tree. Whenever possible, do not remove the needles entirely. Rather, mow them into fine needle particles and let mother nature do the rest.