Shearing West Virginia Balsam (Canaan) and Fraser Fir for Christmas Trees

Special Circular 188

Methods

Trees used in this study were planted in April 1993 at a spacing of 5 feet between trees in rows and 8 feet between rows. The planting was located on a site at The Ohio State University’s Ohio Agricultural Research and Development Center (OSU/OARDC) campus at Wooster. Plugs + 2 planting stock of West Virginia balsam fir of a Canaan Valley seed source and 2 + 2 planting stock of Fraser fir of a Roan Mountain, North Carolina seed source were planted in blocks adjacent to each other. The site was relatively level with well-drained Wooster series and moderately well-drained Canfield series soils.

Weed control in the plantings included preplanting spraying of three-foot wide strips with glyphosate (2.5 pounds a.i.a.), followed by annual applications of sima-zine and atarazine (2 pounds a.i.a. each). Areas between rows were mowed two to four times per year.

In August 1996, trees in the blocks of each variety were divided into sub-plots using a randomized complete block experimental design to provide three-tree plots and four replications of each of the eight treatment combinations shown in Table 1. To conform with the statistical design, treatments were assigned randomly to individual three-tree plots without regard to growth rate, numbers of internodal terminal shoot buds, or branch angles, all of which could substantially affect individual tree response to different shearing treatments.

Table 1. Treatment Combinations for Shearing Study with West Virginia Balsam (Canaan) and Fraser Fir.

Beginning with Treatment 1, trees on individual plots were sheared at the designated times, with leader lengths as indicated, and side limbs sheared to provide uniform shape and taper. When terminals on individual trees were not long enough to permit cutting to the designated length, they were left as long as possible by cutting to a point just above the first, large, internodal bud below the growing tip. In addition, trees in Treatment 4 were fertilized annually in March with ammonium nitrate at a rate of 200 pounds of actual N per acre.

Before trees were sheared the first time, total heights and terminal lengths of trees were measured; after leaders were sheared to appropriate lengths, internodal buds on the cut leaders were counted. When trees were sheared in succeeding years, numbers of internodal lateral limbs that developed from buds on previously sheared terminal shoots were counted and, again, new terminal shoots were measured before shearing to appropriate lengths and bud counts were made on those cut terminals.

In early September of 1997 and 1999, average needle lengths and oven-dry weights of stems and needles were determined from two four-inch-long foliage samples collected from each tree in individual plots. Needles from samples were ground and analyzed for total nitrogen by the School of Natural Resources Service Testing and Research (STAR) Laboratory at the Ohio Agricultural Research and Development Center (OARDC).

In December 1997 and 1999, evaluations were made of the color of the upper surfaces of needles of trees using a subjective rating system of 1 = yellow, 2 = green/yellow; 3 = yellow/green, 4 = green, and 5 = blue/green. In making comparisons, a sample of a single tree that was judged to have yellow/green foliage (rating 3.0) was compared with each individual tree in the study, and a rating was given based on the extent to which foliage color was better or poorer.

At the conclusion of the study in summer 2000, total heights and widths of trees were measured, and foliage density was estimated. In addition, each tree was evaluated for the numbers and locations of minor and major defects (Appendix Table 1) and a USDA grade was assigned to each tree (Appendix Table 2).

Data were analyzed separately for each species using analysis of variance and averages of data for the three-tree plots by OARDC’s Computing and Statistical Services. Significant differences between means were separated using least significant difference tests (L.S.D.0.05).

As noted previously, the plantings of West Virginia balsam and Fraser fir used in this study were in adjacent blocks in the field, an arrangement that would not permit direct, valid statistical comparisons of similarities or differences between the two in effects of shearing treatments. For some variables where there appeared to be ob--vious differences between the two, statistical comparisons were made of “locational” differences between the two blocks, which would include not only possible varietal differences but also site and other factors related to the lack of random assignment of variety-treatment combinations to individual plots.