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

Special Circular 188

Results and Discussion

As noted, data for each variable was analyzed using averages of measurements or evaluations for the three-tree plots in each replication. The data in Tables 2 to 5, in turn, represent averages for the four replications. As may be seen in those tables, there was considerable variation between the overall averages for some data sets and also year-to-year differences in effects of the different shearing treatments.

Additionally, there was considerable plot-to-plot data variation, as indicated by the relatively large standard deviations and ranges in values (minimums and maximums) for some variables. This is not too surprising, given the natural genetic variation in the varieties and differences in soil characteristics within individual plantings.

Tree Heights and Terminal Shoot Growth

Table 2. Heights, Terminal Shoot Lengths Before and After Shearing and Final Heightsof Trees of West Virginia Balsam (Canaan) and Fraser Fir.

Initial Tree Heights

Trees were established and growing well when the shearing study was begun three years after field planting. Total heights of trees of West Virginia balsam fir and Fraser fir averaged 4.13 feet and 4.23 feet, respectively, and new terminal shoot growth, before shearing, averaged 17.3 and 18.4 inches, respectively. There were no statistically significant differences in total heights or unsheared leader lengths for either variety (Table 2).

Terminal Shoot Growth Before Shearing

Figure 3. West Virginia balsam (left) and Fraser fir (right) trees with leaders sheared to 10-inch lengths.

Figure 4. Unsheared West Virginia balsam (left) and Fraser fir (right) trees.

Figure 5. West Virginia balsam (left) and Fraser fir (right) trees with leaders sheared to 12-inch lengths.

Figure 6. West Virginia balsam (left) and Fraser fir (right) trees with leaders sheared using the “progressive” treatment.

Terminal shoot growth before shearing showed decided year-to-year differences. As noted previously, before the first shearing of West Virginia balsam fir trees, unsheared terminal lengths for all trees averaged 17.3 inches, while in subsequent years, they averaged 13.9, 23.6, 15.7, and 20.2 inches, respectively, before the second, third, fourth, and fifth shearings. Similar year-to-year variation was noted for Fraser fir, with lengths of 18.4, 15.7, 22.0, 15.6, and 17.9 inches before the first through fifth shearings (Table 2).

Reasons for this high-low alternating pattern in growth do not appear to be related to treatments. Rather, it may have been related, at least in part, to year-to-year differences in precipitation. Records for the National Oceanic and Atmospheric Administration weather station on the OSU/OARDC campus at Wooster indicate that annual and growing-season precipitation for 1995 (the year prior to the first shearing), 1996, and 1998 were above average, while that for 1997 and 1999 were at or below average. However, for 2000, a year in which terminal shoot growth was good, total precipitation through August (when the study was completed) and for April through August were both well below normal, although there were no periods of prolonged dry weather during the growing season.

There were no consistent effects of shearing on new terminal growth measured the year after shearing was done. In 1997, growth on trees of West Virginia balsam and Fraser fir was significantly greater on unsheared than on sheared trees, but there were no significant differences between trees that had actually been sheared using the different time-length-fertilization treatment combinations. In 1998, 1999, and 2000, there were no significant growth effects between sheared and unsheared trees or between those that had been sheared (Table 2).

In previous research with white pine, Scotch pine, and red pine, it was found that shoot growth the year after shearing was significantly less on sheared than on unsheared trees, and the reduction in growth became progressively greater as trees were sheared later into the summer, autumn, and winter after the “optimum” time in mid- to late-June (Brown, 1960; Brown, 1964; Brown, 1984).

Reasons for the differences between the firs used in this study and the pines in those earlier studies are probably related to the fact that when pines are sheared, the dormant, interfascular buds located at the base of needle fascicles must develop fully, either in the current or succeeding growing season, before new shoots can begin to grow (Figure 1). For West Virginia balsam and Fraser fir trees, internodal buds are already present along the shoots (Figure 2).

Lengths of Sheared Terminal Shoots

At the time of the first and subsequent shearings, average lengths of the main leaders (for three tree plots) of unsheared trees were, in all cases, longer than the lengths to which shoots were supposed to be sheared; however, terminals on some individual trees within plots were not long enough to permit cutting to the lengths designated in the study (Table 1). As noted earlier, when that occurred, the main leaders of those trees were left as long as possible by cutting to a point just above the first, large internodal bud below the growing tip.

As would be expected, because shoots were cut to designated lengths ranging from 10 to 18 inches, depending on the specific treatment and year of the study, there were statistically significant differences between lengths of sheared terminal shoots for trees of both varieties in all years (Table 2).

Final Tree Heights

When the study was completed in the summer of 2000, total heights of trees of West Virginia balsam and Fraser fir ranged from 6.65 and 6.80 feet, respectively, for trees on which leaders were sheared to 10-inch lengths (Treatment 1, Figure 3) to 10.50 and 10.40 feet, respectively, for trees that had not been sheared (Treatment 8, Figure 4). For trees on which leaders were sheared to 12-inch lengths at different times of the year (Treatments 2 to 5), there were no significant differences in total heights of either species, with those of West Virginia balsam fir ranging from 7.23 to 7.51 feet and those of Fraser fir from 7.45 to 7.77 feet (Figure 5).

Total heights of trees of Treatment 6 (sheared to 15 inches each year) and Treatment 7 (“progressive,” with shearing to 18 inches the first year, 14 inches the second, and 12 inches in the third and fourth years) were significantly taller than those of the other treatments in which trees had been sheared (Figure 6), but there was no significant difference between the two (Table 2).

Results of the study indicate that trees sheared consistently to 10-inch leader lengths would begin to reach marketable size, with 6- to 7-foot trees, after five shearings and eight years after planting. For those sheared to 12-inch leader lengths, irrespective of season of shearing or fertilization, trees began to reach the 6- to 7-foot class after seven years in the field, and all trees were in the 7- to 8-foot class after eight years. For trees with leaders sheared consistently to 15 inches and for the “progressive” treatment, trees began to become marketable in the sixth year in the field, and all were in the 8- to 9-foot classes after eight years.

In earlier studies with Scotch and white pine in which leaders were cut to varying lengths over a five-year period, trees with leaders sheared to 10 inches averaged 6.8 and 6.7 feet for white pine and Scotch pine, respectively, while those with leaders sheared to 14 inches averaged 8.6 and 8.2 feet (Brown, 1981).

Numbers of Buds and Lateral Limbs on Terminals

Table 3. Numbers of Buds and Lateral Limbs on Terminal Shoots of West Virginia Balsam (Canaan) and Fraser Fir.

West Virginia Balsam Fir

One of the major factors affecting the quality of single-needled Christmas trees is the number of internodal buds along the terminal shoots between the major whorls of limbs and the number of lateral limbs that develop from those buds (Table 3, Figure 2). For the West Virginia balsam fir trees used in this study, the number of internodal buds present on cut terminals averaged from 1.8 to 2.6 per inch over the five-year shearing period.

In three of the five years, there were statistically significant differences between treatments in average numbers of buds on shoots; however, there were no consistent patterns in numbers related to whether terminals were or were not cut, the lengths to which leaders were sheared, time of shearing, or fertilization. For the different years, lateral limbs on sheared shoots averaged slightly less than numbers of internodal buds; this same pattern of fewer limbs than buds on trees receiving different shearing treatments was also evident, although there were some exceptions for different treatments and/or years.

Fraser Fir

The numbers of internodal buds and limbs on terminals of Fraser fir were consistently lower than for West Virginia balsam fir, with average numbers for the different years ranging from 1.4 to 1.7 per inch (Table 3, Figure 2). Similarly, numbers of internodal lateral limbs were generally less, averaging from 1.0 to 1.5 per inch. This pattern of fewer limbs than buds on trees receiving the different treatment combinations was also evident, although again there were some exceptions.

A comparison of the differences in buds and lateral limbs on West Virginia balsam and Fraser fir (as described in loca-tional effects in the Methods section) indicated that those differences were probably statistically significant. Other studies also found higher numbers of buds and lateral limbs on terminal shoots of West Virginia balsam than on Fraser fir (Brown, 1983b; Brown, 1999).

Foliage Characteristics of Trees

Needle lengths, foliage weights, foliar N content of needles, and foliage color of trees of both West Virginia balsam and Fraser fir showed no significant effects related to time of shearing or lengths to which terminal shoots were sheared.

However, fertilization with 200 pounds of nitrogen each year did affect foliage characteristics of trees. Needle lengths were significantly longer in the second and fourth years of the study for both varieties, with those on fertilized trees averaging 24.1 and 23.8 mm in the two years for West Virginia balsam fir and 21.2 and 21.3 mm for Fraser fir. On unfertilized trees, needles were generally 2 to 3 mm shorter for West Virginia balsam and 1 to 2 mm shorter for Fraser fir.

Similarly, weights of twigs and needles were consistently heavier, although not statistically so, on fertilized trees. For both species, foliar N content was significantly higher on fertilized trees in both years. In addition, colors of the upper surfaces of needles of both species were significantly better on fertilized trees, averaging from 4.00 to 4.15 (at or slightly above the “green” rating), while on unfertilized trees color ranged from 3.48 to 3.60 (yellow/green) for West Virginia balsam and 3.69 to 3.83 (yellow/green to green) for those of Fraser fir (Table 4).

Table 4. Foliage Characteristics of Trees of West Virginia Balsam (Canaan) and Fraser Fir.

In previous studies, nitrogen fertilization of Fraser fir (Brown, 1976; Keller, 1980) and West Virginia balsam fir (Brown, 1998a; Brown, 2000a) did not significantly affect shoot growth of trees but did result in increased needle lengths, foliage weights, foliar N content, and improved foliage color.

The color of the lower surfaces of needles of trees, particularly as influenced by the number and coloration of stomatal bands, can have a distinct influence on the appearance of trees. That characteristic was not evaluated as part of this study. However, it was observed that the underside of the needles of Fraser fir had a distinctive and consistently “bluish” appearance, while those of West Virginia balsam fir were generally more variable, with color ranging from a “grayish” to “moderately bluish.” Similar results have been noted in other studies (Brown, 1998a; Brown, 1999; Brown, 2000a).

One other result of interest was average weights of stems and needles. Overall averages for stems of four-inch-long samples of West Virginia balsam were approximately 4.5 grams in each of the two years when samples were collected, as compared to more than 5.5 grams for Fraser fir. For needles, average weights (approximately 3.5 grams) were considerably less for West Virginia balsam than those of Fraser fir (more than 4 grams), despite the fact that needles of West Virginia balsam trees were longer (Table 4). These heavier weights, particularly for Fraser fir twigs, may in part account for the sturdier, less flexible limbs on Fraser than on West Virginia balsam trees.

Tree Quality and USDA Grades

Tree Taper

Taper (width/height) is one of the factors considered in determining the USDA grade of Christmas trees. For both West Virginia balsam and Fraser fir, the average taper for trees in all treatments, including those that were unsheared, was within the 40 percent to 100 percent range required for the U.S. Premium grade. In addition, standard deviations, a measure of variation within treatments, were relatively small, averaging just 8 percent of the overall mean for each species (Table 5, Appendix Table 2).

Table 5. Tree Quality and USDA Grades for West Virginia Balsam (Canaan) Fir and Fraser Fir.

For individual shearing treatments, highest taper was found on trees on which terminals had been sheared to the shortest (10-inch) lengths (Figure 3), while the nar-rowest taper occurred on trees on which terminal shoots had been sheared using the “progressive” treatment (Table 5, Figure 6). At least some of these differences were related to the five-foot spacing within rows at which trees were planted.

To provide uniform taper and density, it was necessary to shear trees to a final width of approximately 5 feet; thus, the shorter the terminals and total heights of trees, the greater the taper. Unsheared trees were the exception; although they were the tallest, limbs in the lower whorls often overlapped those of adjacent trees, resulting in somewhat higher taper but uneven lengths and incomplete whorls that resulted in many other grading defects (Figure 4).

Tree Density

Figure 7. Uneven density in foliage of Fraser fir tree.	Figure 8. Small holes in foliage of West Virginia balsam fir tree.

Figure 9. Noticeable holes in foliage of West Virginia balsam (left) and Fraser fir (right) trees.

Figure 10. Multiple leaders on West Virginia balsam (left) and Fraser fir (right) trees.

To qualify for the USDA Premium grade, density of trees of Fraser fir must be at least 70 percent, while for West Virginia balsam it must be at least 80 percent (Appendix Table 2). In this study, densities of trees of West Virginia balsam fir and Fraser fir were approximately the same, with overall averages of 72.3 and 69.2 percent, respectively.

For Treatments 1 to 7 for which trees had been sheared, densities were highest where terminals were cut to 10-inch lengths (Figure 3), with an average of 85.3 percent for West Virginia balsam and 79.8 percent for Fraser fir, and were lowest (70.0 and 68.5 percent, respectively) for trees which received the “progressive” treatment (Figure 6).

For both species, there was considerable tree-to-tree variation within treatments, as indicated by the relatively high standard deviations of 21 percent of the overall averages (Table 5). Average density of unsheared trees (Treatment 8) for both species was approximately 30 percent which, independent of other factors, would give trees a Cull grade (Appendix Table 2, Figure 4).

Numbers of Defects per Tree

The USDA standards for evaluating quality of Christmas trees use several types of defects and the extent to which they affect the appearance of trees to establish U.S. Premium, No. 1, No. 2, and Cull Grades (Appendix Table 2). Numbers of “minor” defects were generally slightly but not significantly higher on trees of West Virginia balsam than on those of Fraser fir, with overall averages of 1.54 and 1.45 per tree, respectively. Similarly, except for those trees on which terminals had been sheared to 10-inch lengths, minor defects for individual shearing treatments were generally slightly higher on trees of West Virginia balsam fir, with ranges in numbers from 1.60 to 2.20 and 1.50 to 2.00 for the two varieties (Table 5, Appendix Table 1).

Although the types of minor defects of trees are not detailed in Table 5, much of the difference between the two varieties was related to the lower density requirements for Fraser fir. Other minor defects included uneven density (Figure 7) and small holes or gaps in the foliage (Figure 8). As shown in Table 5, there was considerable tree-to-tree variation in numbers of minor defects as indicated by the very large standard deviations of 64 percent for West Virginia balsam and 68 percent for Fraser fir.

The numbers of “noticeable” or major defects was consistently lower on sheared trees of West Virginia balsam than on Fraser fir, with averages of 1.54 and 2.21, respectively, for the two varieties (Table 5, Appendix Table 1), with defects on un-sheared trees accounting for many of the problems in “average” tree quality. Within each variety, tree-to-tree variation in noticeable defects was very great, as indicated by the large standard deviations of 227 and 178 percent of the overall means for West Virginia balsam and Fraser fir, respectively.

For trees that were sheared, noticeable defects ranged from 0.00 to 0.50 and 0.30 to 1.03 per tree, respectively, for West Virginia balsam and Fraser fir, with lowest numbers for trees on which terminal shoots were cut to 10-inch lengths. Differences in noticeable defects between West Virginia balsam and Fraser fir were primarily related to higher occurrences of moderately uneven density (Figure 7) and holes or spaces that were considerably out of proportion with uniform branch characteristics on trees of Fraser fir (Appendix Table 1, Figure 9).

The higher occurrence of irregularities in the foliage of Fraser fir was probably related to differences in numbers of inter-nodal limbs (discussed earlier) and branch angles on trees of the two varieties. Although it was not measured in this study, previous research found that trees of West Virginia balsam fir generally had more “upswept,” ascending branch angles than those of Fraser fir (Figure 2) which tend to cover the terminal shoot, thereby helping to reduce “holes” and other irregularities in foliage density that might decrease tree grade.

Higher numbers of internodal limbs and more ascending branch angles on trees of West Virginia balsam fir can also create potential problems. Multiple leaders and multiple main stems are other defects that affect Christmas-tree quality. None of the sheared trees in the study had those defects because care was taken to leave only one leader on trees. However, it was observed that trees of West Virginia balsam fir had a tendency to have more multiple leaders before trees were sheared than did those of Fraser fir and care should be taken to remove them (Figure 10).

USDA Grades of Trees

Figure 11. Trees of West Virginia balsam fir having (left) a short terminal shoot and slightly ascending branch angles for lateral limbs and (right) a longer terminal shoot and pronounced ascending branch angles for later

In analyses of data for USDA grades for trees (U.S. Department of Agriculture, 1989), those graded as Premium, No. 1, No. 2, and Cull were assigned values of 4, 3, 2, and 1, respectively; thus, the higher the value, the better the tree (Table 5, Appendix Table 2). The overall average USDA grade for trees of West Virginia balsam fir (3.10) was slightly higher than that for Fraser fir (2.93) — with both being near the USDA No. 1 grade of 3.0.

For trees on which terminals were sheared to different lengths, average grades were consistently better for West Virginia balsam fir than for Fraser fir, with ranges from 3.10 to 4.00 and 2.92 to 3.60, respectively, with highest average grades for trees with terminals sheared to 10 inches - the treatment for which there were the fewest number of minor and noticeable defects (Figure 3). Average grades of sheared trees were lowest for trees sheared using the “progressive” treatment for which average numbers of minor and noticeable defects were highest (Figure 6). All unsheared trees in the study were graded as Culls (1.0) because of a variety of multiple defects on individual trees (Table 5, Figure 4).

For trees on which terminals were sheared to 12-inch lengths at different times of the year (August, November, and March), with or without nitrogen fertilization, average grades for both varieties were highest for trees sheared in August and lowest for those sheared in March (Table 5). As noted previously, nitrogen fertilization improved needle lengths, twig weights, and foliage color of trees of both varieties.

Figure 12. Seven-year-old West Virginia balsam fir produced from a rapidly growing tree on a good site and having good bud set and strongly ascending lateral branches.

However, because the overall foliage quality of trees was judged to be within “characteristics typical of the species” as used in the grading standards (Appendix Table 2), those improvements were not reflected in the grades assigned to individual trees and, as a result, there were no apparent differences in average grades of fertilized and unfertilized trees that were sheared in November.

Differences in “average” grades of trees were reflected in the proportion of trees having different USDA grades. For West Virginia balsam fir, 44.9 percent of individual trees were graded as Premiums, 32.2 percent as No. 1s, 10.4 percent as No. 2s, and 12.5 percent as Culls. For Fraser fir, comparable values were 31.3, 44.2, 12.0, and 12.5 percent.

For both varieties, the highest number of Premium trees was recorded for those on which terminals were sheared to 10-inch lengths - 100 percent for West Virginia balsam and 58.5 percent for Fraser fir. None of the individual trees that were sheared were graded as Culls, while all unsheared trees were Culls (Table 5).

Higher USDA grades for trees of West Virginia balsam fir were a reflection of the types of “minor” and “noticeable” defects on trees and the numbers and locations of those defects on the four different “faces”of trees. As outlined in Appendix Tables 1 and 2, U.S. Premium trees can not have any noticeable defects and not more than two minor defects, one on three adjacent faces and a second on the fourth face. To be graded as a U.S. No. 1 tree, there can be one noticeable defect on one face and not more than two minor defects on the remaining three faces.

As discussed previously, sheared trees of West Virginia balsam fir had fewer noticeable defects than did those of Fraser fir and those that did occur were more commonly confined to only one face. Additionally, although trees of West Virginia balsam fir had slightly higher numbers of minor defects, they tended to be more evenly distributed over the four faces (Table 5).