Fig. 37: Diagram showing relative taper of Christmas trees. L. to R., candlestick, preferred and flaring.
Shearing is the most important cultural practice involved in growing quality Christmas trees. Of all the practices that can be employed by a grower, shearing probably gives the greatest return for labor invested. Consumers demand a dense, well-shaped tree with relatively uniform taper.
The practice of shearing involves controlling growth in height and width by cutting off the tip of the leading shoot (leader or terminal) and the ends of the lateral branches to develop the desired conical shape. The purposes of shearing are: 1) to control tree height and width and develop desired taper and shape; 2) to stimulate increased numbers of buds and bud development, thus increasing the number of branches and foliage density (pines) and 3) to correct branch deformities and insect and disease damage and to remove competing multiple leaders.
Trees are sheared to the shape of an inverted ice cream cone with a wide base and a uniform taper to the tip of the tree. "Taper" means the relationship of the width of the tree to its height and is determined by dividing the width of the tree at its base by tree height and multiplying the result by 100. The ideal tree shape is about two- thirds as wide as it is high, or a 66-2/3 percent taper. A tree 6 feet tall and 4 feet wide at the base has this percentage taper. United States standards for grades of Christmas trees (Table 7) define taper standards as follows (Fig. 37):
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| Fig. 37: Diagram showing relative taper of Christmas trees. L. to R., candlestick, preferred and flaring. |
| Table 7: Summary of United States Standards for Grades for Christmas Trees | ||||
|---|---|---|---|---|
| Factor | U.S. Premium | U.S. Choice or U.S. No. 1 | U.S. Standard or U.S. No. 2 | |
| Foliage | Fresh, clean healthy, well trimmed | Fresh, clean, healthy, well trimmed | Fresh, fairly clean, well trimmed | |
| Density | Medium | Medium | Light | |
| Taper | Normal | Normal | Candlestick, normal or flaring. | |
| Faces | 4 free from damage | 3 free from damage | 2 adjacent free from damage | |
| Definitions of terms: | 1. Fresh needles pliable and generally firmly attached. | |||
| 2. Clean: practically free of moss lichens vines, etc. | ||||
| 3. Fairly clean tree moderately free from moss, lichens, vines, etc. | ||||
| 4. Well trimmed all barren branches below first whorl removed and butt of trunk cut smoothly at approximately right angle to trunk. | ||||
| 5. Healthy: foliage has thrifty, fresh, natural appearance. | ||||
| 6. Density amount of foliage present, determined by number and size of branches, distance between whorls number and arrangement of branchlets, extent of internodal branching, needle arrangement, needle length, etc. Species differ in these characteristics, and density is judged on the basis of "species characteristics." | ||||
| 7. Taper: relationship of tree width to height, expressed as % | ||||
| Pines | Spruces, firs, Douglas-fir | |||
| Normal | 40 to 90% | 40 to 70% | ||
| Flaring | more than 90% | more than 70% | ||
| Candlestick | less than 40% | less than 40% | ||
| 8. Faces refers to visible surface area of tree, with four faces, each consisting of one-fourth of the surface area of the tree. | ||||
| 9. Cull: any tree that does not meet the above standards. | ||||
Pines are usually grown with a taper in the range of 60 to 90 percent, while for the spruces and firs, it is usually from 40 to 70 percent. As a grower gains experience, the market determines the amount of taper. Some buyers prefer "fat" trees while others prefer a more normal taper. Shearing controls the taper.
After planting, seedlings or transplants usually undergo a slow-growing initial establishment period of one to three or more years. During this time, root systems are developing and adjusting to their new environment, and terminal elongation is usually less than 12 inches. During the second or third year in the field, pine leaders normally start to grow more rapidly. Shearing should be initiated at this time. If it is not, excessively long internodes ("goosenecks") will develop. The combination of "goosenecks" and varying length laterals give trees an open, irregular appearance not representative of a quality Christmas tree (see Figs. 38 and 39). Spruces and firs go through a process called "planting check." Terminal growth elongation usually resumes more slowly after planting. Shearing on spruces and firs may have to be delayed until the fourth or fifth year in the field unless good grass and weed control practices are initiated and maintained. These time periods are guidelines only! Once terminal elongation exceeds 10 to 12 inches, shearing must be started and continued every year, if necessary, until the trees are harvested as quality trees (Figs. 5 to 12).
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Fig. 38: Unsheared Scotch pine showing variations in outline and density. | Fig. 39: Unsheared Norway spruce showing variations in outline and density. |
Before shearing techniques are discussed, it is necessary to illustrate or define some of the common terms used in Christmas tree terminology (see Fig. 40). Pines, spruces and firs produce a terminal stem called the leader and a major whorl of lateral limbs at the base of the leader each year. The point of attachment of the limbs in the whorl to the stem of the tree is called a node. On spruces and firs, a number of buds normally develops along the leader between the node and the terminal or end bud. The buds that develop along the leader of spruces and firs are called internodal buds and develop the next year into limbs that contribute strongly to foliage and limb density. An internode is the space on the stem between two nodes. Control of the internodal distance is critical to shearing success.
| Fig. 40: Diagram of tree, including terms important to understanding Christmas tree shearing techniques. |
Species grown for Christmas trees in Ohio can be divided into two broad groups as far as proper shearing procedures are concerned: (1) the multi-needled pines with two to five needles in each cluster (bundle or fascicle) on the stem or branch and (2) the single-needle conifers such as spruces, firs and Douglas-fir. Shearing procedures and timing are different for the two groups.