Can You Prune an Arizona Spruce?

Identification

• Two species of spruce are native to Arizona. One is the Engelmann spruce (Picea engelmannii), hardy in U.S. Department of Agriculture plant hardiness zones 2 through 5 and native to the western United States. The Colorado blue spruce (Picea pungens), also native to Arizona, will grow in warmer areas, doing well in USDA zones 2 through 7. Engelmann spruce grows to between 70 and 100 feet and has dark or bluish green foliage, while Colorado blue spruce is shorter, only 30 to 60 feet, with blue or silver needles. Pruning instructions are similar for all spruces.

Pruning for Compactness

• If you wish to thicken your tree’s canopy, you should prune in spring or summer after the spruce tree has already grown new foliage. This process is called candling for the lighter portions that form on the ends of the branches, which is the new, immature foliage. Look for this lighter growth, which you can safely prune off. Prune down to half the height of the new growth, which will encourage the tree to regrow in a bushier fashion. Never prune off a branch below that year’s growth, as older growth turns brown and does not grow back.

Pruning for Shape

• If, on the other hand, your spruce’s canopy is too thick, you can remove branches to thin the overall appearance. Be aware that if you prune off hardened, older wood, that part of the tree will not grow new shoots. Therefore you can prune lighter new growth off of branches to thin them, but should not cut through the center of a thick branch at any point except flush against the trunk. Doing so will thin the canopy without leaving an ugly dead stick in the tree’s otherwise symmetrical growth habit. Carry this out in late winter, while the tree is still dormant.

Techniques and Precautions

• Spruce trees posses an upright, symmetrical growth habit and do not generally take kindly to shearing. Prune for shape and compactness and leave it at that. Always use very sharp tools, and clean the blades by swabbing with rubbing alcohol before and after the job. If you are pruning out diseased branches, you may do this at any time of the year. When working with disease, be sure to clean the blades in between each cut to avoid spreading the pathogen.