Shearing Christmas Trees
Shaping or shearing of conifers is required to produce a salable Christmas tree in Iowa because consumers demand that the tree have uniform spacing between branches, dense foliage and a symmetrical shape.
During the first 2-3 years after planting, shearing involves pruning of multiple leaders. Shearing for shape and density begins as soon as annual growth rates exceed 10 to 12 inches per year. Shearing then continues every year until the tree is marketed.
Correct timing is critical for proper shearing. Spruces and firs can be sheared any time during the year, but the best time to shear is from September to March. This extended shearing time is possible because these species produce auxiliary buds along the stems and branches as the tree grows. These buds are fully developed and form bud clusters whenever the stem or branch immediately above them is removed.
Pines are sheared during the active growing season, usually June through July. Pines do not form axillary buds, and will form a cluster of buds when sheared at the correct time. If sheared too early, growth may continue resulting in too much distance between branches; pines sheared too late may result in no bud set, fewer buds or dieback of the terminal leader.
During shearing, cut all side branches necessary to give the tree the desired shape and taper. Desired taper varies from 1/2 to 2/3 as wide as the tree is tall. Shearing should be done only on the current years growth.
Several different tools can be used for shearing including hand clippers, hedge shears, power trimmers and shearing knives. Hand clippers are slow but precise and are most useful when shearing spruces or firs when shearing back to existing buds. Hedge clippers are faster but require more energy to use for long periods of time. Shearing knives, sharp, smooth or serrated blades 12-20 inches long, are perhaps the fastest but most hazardous; guards must be used for maximum safety.