Question
We planted a dwarf blue spruce last year  in the Invermere, British Columbia are and this year it is looking great with lots of new growth. We do want to shape the tree and keep it under control. When is the best time to trim it? spring, summer or fall?

Answer
One great asset to having a dwarf Alberta spruce in the landscape is that they very rarely need pruning. They naturally maintain their shape. Their needles are thin, but grow very densely on the tree, giving it a very solid and full appearance. The branches also persist all the way to the ground, without the lower limb dieback common to some evergreens as they age.

There is one significant time when a dwarf Alberta spruce will need pruning. The dwarf Alberta spruce is essentially a mutant of the much larger Alberta White spruce. Occasionally, especially in older trees, new growth on branches will change in appearance, the needles appearing much longer and growing much faster. These sections are called "revertants" meaning that on the DNA level, cells are losing the dwarf mutation and reverting to the Alberta White spruce form, the "original" or "wild type" form of the plant.

If you wish to keep your dwarf Alberta spruce a dwarf, any revertant sections need to be removed promptly. Prune just below the area where the revertant branch form begins. There is not a real time to prune these wild growing branches anytime is ok. But a light trimming should be done in the early spring.