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No, It Is Not a New Pest

Regular readers of the column get a heads-up on new pests as they appear in Pennsylvania. The past several years, the talk of the town has been the likes of the spotted lanternfly, allium leafminer, and boxwood blight. Now the question has been broached about the weird growths of some dwarf Alberta spruces in central Pennsylvania. While some organisms can cause plants to appear deformed or develop abnormally (think black knot on cherry, the galls of cedar apple rust, or bagworms), the dwarf Alberta spruce issue is another matter.

To understand what is happening, we must first understand the origins of this small conifer. Most of us are familiar with white spruce (Picea glauca). It is a tree that can grow up to 100 feet. In the early 1900s, two horticulturists were wandering around the Alberta, Canada region and noticed some dwarf white spruces. Something they had never seen before, they took back into the U.S. and found that this dwarfing characteristic could be propagated. It was also determined that these small spruces (Picea glauca var. albertiana f. conica) were actually naturally-occurring mutant of the white spruce.

The problem occurs as these dwarfs age and have been in the landscape for several years. Some branches will revert back or mutate back to their normal parental form. This is noticed when it appears that a tree is growing out of the tree. It can simply be left alone as it is not a pest and interfering with the plant’s normal growth and activity, This lack of action can cause the beauty of the dwarf spruce to be greatly diminished.

In addition, the new branch will start to grow like its parent and reach over 80 feet in height. This can be a problem as dwarf spruces are placed in areas that are tight or require small plants for the design. A 80 foot tree can really throw things off.

Do not remove your small conifer, thinking it is now useless. Follow the abnormal branch growth back to the trunk and simply prune it out. This should correct your problem and allow the dwarf Alberta spruce to provide many more years of beauty

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