Question
What time of year can you trim leland spruce ? I want to just trim some branch tips .
also, what time of year is best to trim boxwoods ?
thank you

Answer
Sun-loving conifers, those whose needles all need sun, can be pruned annually, but only gently within the living green foliage. This type of ever-green does not have green needles in the interior of the plant. Most do not even have growing buds on interior branches. As a result, if you prune that plant hard, into old wood, once it has become extremely over-grown, you will end up with an ugly brown bare spot in your tree or shrub. Most junipers and arborvitae fall into this category.

As for timing of pruning, there are a few factors to consider. First, diseased, dead or dam-aged branches should be pruned out at any time. Second, pruning stimulates soft new growth, which is easily damaged by cold temperatures and harsh winds. Therefore, if pruning is done too late in summer (before new growth has a chance to harden off) or too early in spring (when growth starts before the harsh winter ends) the tender new growth can be damaged. Third, some evergreens produce a large amount of sap when actively growing, typically in early spring and sometimes with another burst of growth in summer. Do not prune at these times because the plant will "bleed" profusely.

Trim the sides of Leyland cypress trees every year (July is often recommended as a time for general pruning). After the leader has reached the height you want the tree to retain, make a pruning cut a few inches below that (which will leave room for the vertical growth of minor branches) to preclude any further significant upward growth.

For boxwoods major pruning should be performed in late winter or early spring.