One of the more important cultural practices in growing quality Virginia pine Christmas trees is shaping. Shaping is any process which removes limbs, branches, or new growth with the purpose of improving overall tree quality. Other terms are also used to more specifically define the shaping process. Pruning removes an entire leader or lateral limb. Shearing refers to cutting new growth to improve form and density. Usually, pruning involves correcting a problem, while shearing provides desired form.
Consumer surveys indicate that the most important characteristic in selecting a Christmas tree is shape. Height is usually considered the second most important characteristic. To grow high-quality choose and cut trees there must be: 1) controlled tree height and width; 2) symmetrical form and uniform density; 3) corrected insect damage; and 4) the removal of lower branches to form a "handle."
Initial growth in the spring consists of shoot elongation (on both the terminal leader and lateral branches), followed by a cessation of growth, often referred to as bud "setting." The normal bud set consists of a terminal bud, surrounded by lateral buds. As each growth flush occurs, the terminal bud produces more growth than do lateral buds.
Many Christmas tree species have only one growth flush each year. Virginia pine is an exception and may have from two to four growth flushes during the growing season, depending upon rainfall, temperature and fertility.
At the base of each group (fascicle) of needles is a dormant and undeveloped fascicular bud. Fascicular bud development is normally suppressed by growth hormones produced in terminal and lateral buds.
When those terminal and lateral buds are removed, fascicular buds are stimulated to grow and develop into shoot buds. The effect is most noticeable on dormant buds just below the cut. The number and vigor of buds that develop depend primarily upon stem diameter, location on tree (terminal or lateral branches) and time of year when cut.
Like most species, shaping requirements for Virginia Pine vary according to site fertility, climate and market preference.
Generally, corrective shaping (pruning) should be done during the dormant season, but can be done at any time of the year. In the first growing season after planting, some seedlings may continue growing, with new growth reaching 15 to 18 inches before budset in the fall. These trees should be pruned back to 10 to 12 inches.
In late winter of the second year, corrective pruning of multiple leaders and excessive lateral growth should be completed. This is also a good time to remove the lowest branches to begin forming the "handle."
Trees should be inspected again in May of the second year after the first flush of growth for corrective pruning and possible shearing. If terminal growth is eight inches or less, shearing is not required. Trees should be checked again in early August of the second year for corrective pruning.
Trees will probably need shearing to begin developing a conical shape after the first flush of growth of the third year. This shearing should be done during the first three weeks of May.
As a guide to proper shearing time, the leader should be near its maximum diameter and beginning to "harden off." A general rule of thumb is to begin shearing when needle length on new needles reaches one-half to two-thirds the length of previous needles (last flush or last year's). A second guide is when small red "veins" appear to form in the new stemwood. Another, but lighter shearing is needed in early August.
The same procedures should be followed each year until trees reach marketable height. A top area "touch up" may be needed in November on trees to be harvested that year.
Shearing should be accomplished each year, once it has been started. If a year is missed, the correct form and density are almost impossible to achieve.
Timing of shearing is critical. Trees sheared too early may form fewer buds and have reduced growth. Trees sheared too late may not have sufficient time to form new shoots for the following year. If anything, Virginia pine can tolerate early shearing better than shearing that is too late, due to the multiple-flush growth pattern.
In shearing, the leader and top whorl are extremely important in building the basic framework of a quality tree. Leader growth on Virginia pine should be held to no more than eight inches. At least four lateral branches at the base of the terminal growth are desired. The terminal leader should be pruned to maintain tree height and width. A 45° angle cut on the leader promotes dominance of one of the fascicular buds. The leader should not be cut below existing needles, as new buds will be formed within those fascicles.
Hand pruners are most often used to clip the terminal and branches in the top whorl. Those branches in the top whorl should be cut to length of the terminal leader. This procedure assures that the desired terminal will remain dominant to the side branches.
A guide for shearing the side of the tree can be developed by drawing an imaginary line from the terminal, with the desired taper to lower limbs. All branches extending beyond this imaginary line should be sheared.
Taper is the relationship between tree height and width of bottom branches. Most consumers prefer trees with a 60 to 70% taper. A tree 8 feet tall with a 70% taper would have a lower branch width of 5.6 feet. In shearing Virginia pine it is a good idea is to start with a broad base and gradually reduce the taper in subsequent shearing. It is difficult to obtain uniform lower limb development if trees are too narrow. Virginia pine does not tolerate shading well, and growth and bud development is not as vigorous in the lower tree portion as in the upper portion.
"Handles" should be completed at least two years prior to harvest. Providing a handle permits easier mowing, herbicide application, harvesting, and fitting into a Christmas tree stand. For consistency with other species, a handle should be no less than one inch or more than 1.5 inches per foot of tree height.
Growers use a number of different tools to prune and shear Christmas trees. The selection is determined by cost, size of trees, crew experience, safety considerations, etc. There is no "best" tool, as each has its own advantages and disadvantages.
Hand pruners are used to remove defects, large limbs and multiple terminals. Pruners also are desirable for developing handles on small trees. Hedge shears are used by some who are concerned with safety, as there is less chance of injury with these tools than with other pieces of equipment. Hedge shears usually require a greater amount of time than other tools, especially for inexperienced workers.
Motorized shearing devices are available which are fast and effective, particularly for larger trees. Production rates with these units have been reported to be two to three times greater than with knives, but workers tend to tire quicker. Many of these machines are somewhat awkward and may be difficult to maneuver on steep terrain. Safety should be the primary concern when using any motorized equipment.
Most Christmas tree growers use razor-sharp, lightweight knives with 14- to 16-inch blades to shear Virginia pine. Knives are relatively inexpensive, production rates are adequate, and workers can be trained relatively quickly to produce good quality trees. Shearing knives are DANGEROUS, and safety is most important. General guidelines for using knives are:
- Leg guards should be used at all times.
- Knives should be swung away from the body. A worker should never "cross back" to shear a previously missed branch.
- Workers should not work on the same row or even adjacent rows. They should be spaced so that work areas do not overlap.
- A protective glove should be worn on the non-shearing hand. Some workers prefer to use special improved-grip gloves on the shearing hand to lessen the chance of dropping the knife while shearing.
- The non-shearing hand should never be used to move or hold branches while shearing. Many workers hold pruners or other devices in this hand to keep it away from the knife.
- Eye protection is recommended (with all equipment, not just knives).
- Knives should never be thrown or used in a reflexive action, such as if the worker is attacked by bees or wasps.
- There is no substitute for well-trained workers and good supervision.
Tools should be kept clean and sharp in order to function properly. Tools in good condition will make a clean cut on the tree, rather than bruising or tearing plant tissue. Dull or resin-coated knives tend to beat off the needle fascicles resulting in fewer buds being formed. Sharp tools also help reduce worker fatigue, a major factor in farm accidents.
Shaping is an important part of preparing Christmas trees for sale. If done properly, shaping will provide:
- A single main stem that is straight as possible.
- A symmetrical and balanced form.
- Full and compact foliage with no voids.
- A taper with the base of the tree approximately two-thirds the height of the tree.
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Publication date: April 23, 2014