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Pruning and training apple trees, basic principles and new strategies to improve fruit quality in modern plantings .
Why prune and train? An apple orchard is a solar collector, fruit trees convert sunlight energy to chemical energy then utilize this energy to manufacture a nutritious food. Apples.
Before beginning work on the tree architecture and in an orchard block, it is important to review why we prune and train for trees. There are two main considerations, the total amount of light intercepted, influences crop yield. And the distribution of light throughout the canopy determines the location of fruit and its quality.
The primary goal of pruning and training fruit trees is to improve sunlight distribution.
Apple leaves almost harvest at least 30 percent of the sunlight available on a sunny day to operate at full capacity and for fruit to obtain maximum size, color, and sugar levels. Where as with a grain crop, 100% sunlight interception is optimal. With apple trees, fruit quality must be balanced with total crop yield.
Optimal sunlight interceptions closer to 70 percent. In this way leaves throughout the canopy operate with adequate light. Light can move about four feet into a tree canopy before it becomes limiting. Strategic pruning and training create windows into tree canopies to let sunlight in. This is an important step to grow big sweet apples with attractive skin color. Other goals to consider are tree size control and increased yeild efficiency. Crop load reduction, fruit spur renewal, improved air movement and disease control, limb selection in positioning, shaping canopy to desired form. First, controlling tree size and increasing yield efficiency. Pruning is a dwarfing process and can be used to maintain a tree in its allotted space in an orchard row, optimizing pounds of fruit per pounds wood equates to optimum yield efficiency.
Second, crop load reduction. Since an apple tree will usually set more fruit than it can support, partial crop thinning can be accomplished by removal of fruit bearing surfaces.
Third, fruit spur renewal. Fruit size and quality decline on old spurs purning stimulates new wood with young spurs.
Next, improved air movement which promotes better drying conditions and spray penetration. These help to reduce damage caused by insects and disease. An open tree canopy is important component of a successful integrated crop management program.
Fifth, when selection in positioning remove the damaged in diseased branches.
Also limbs that are more than a half the diameter of the truck at the point of attachment. These branches tend to shade lower portions of the canopy, limbs with wide crouch angles have the best balance between shoot growth and fruit production.
Any final goal of pruning and training apple trees is to shape the canopy to the desired tree form. In apple orchards trees are trained to a conical or pyramid shape and most training systems.
How we make the windows into a fruit tree is important. It's essential to understand when to use various pruning and training strategies.
There are two types of pruning cuts, heading and thining. A fruit tree will respond very differently to the different cuts. With a heading cut the terminal portion of a branch, limb or shoot is removed.
The main effects of the cut are, an increased number of shoots, increased length of shoots, more upright growth, reduced numbers of fruit spurs, and a denser canopy with reduced light levels. Heading cuts should be reserved for training young trees and for limb renewal on mature trees. If there is a portion of a tree canopy where increased branching is desired use a heading cut. To make a heading cut, position pruner blades at an angle about a quarter inch above a bud position to grow in a desired direction. Pruning tools should be kept sharp so that the cuts can be made quickly and smoothly.
One type of heading cut that should not be used on apple trees is a bench cut.
It is preferable to use training aids to adjust lim angles. With the thinning cut an entire branch, limb, or shoot is removed. Growth is stimulated at the site of the cut but to a much lesser extent than with the heading cut. The main response is fewer shoots which resulted in more open canopy and improved light distribution. Thinning cuts are utilized in both young and mature trees to maximize light interception, crop production, and fruit quality.
To properly thin out a shoot make a pruning cut at its base just outside the collar.
Notice the swollen area. Keeping the color intact will result in an improved healing response. To encourage the development of a new branch at the site of the cut a bevel or dutch cut is used. This is an angled cut that preserves the latent bud on an underside of the shoot that will likely grow into a renewal one.
Various training strategies can be used to open windows and fruit tree canopies.
The principal to keep in mind is that a very upright shoot will tend to be overly vigorous and will not bear much fruit creating poor light conditions. At the other extreme, a shoot or branch in a flat orientation will produce an excessive number of fruit and shoot growth will be minimal. The ideal branch angle various with apple variety and training system but is generally between 50 to 75 degrees from vertical for permanent scaffolds. A scaffold limb spread to a wide angle will have better balance between vegetative growth and fruit production.
Temporary branches in upper tiers of an apple tree or train to horizontal positions to induce fruiting. A second or third tier branch that is overly vigorous should be bent to below horizontal. Popular training systems in newer orchard blocks for the vertical axis and the state central leader, both used with size restricting rootstock. In older blocks common systems are the freestanding central leader and the multiple leader upside-down pyramid system.
Pyramid or cone shaped trees either the vertical axis or the central leader system intercept adequate sunlight while allowing good light distribution to the lower canopy. An orchard of pyramid shaped trees is arranged just like an efficient solar panel system, the top of each panel allows light to reach the base of each panel.
Large freestanding central leader train trees and especially multiple leader train trees have poor light conditions it is crucial to create windows of light by thinning out each scaffold in relation to itself and to the others around it.
Developing a pyramid-shaped canopy requires patience, at some point as the tree reaches five to seven years of age, the leader will grow taller than planned final height of the mature canopy.
It then becomes a temptation to attempt to contain tree height by shortening the leader, do not give in to the temptation, wait until leader has become fruitful and its growth has slowed before heading it. Often this will not occur until the 7th leaf. Then shorten the leader by cutting back to a fruitful side branch.
The leader must be allowed to grow taller than the final tree height for a year or two. Cutting too soon will lead to delayed fruiting and more vigorous re-growth, some refer to this management technique as crop and flop.
Pruning becomes more intensive with multiple leader trees. The greatest challenge in this canopy shape is to prevent the upper branches with good light exposure from outgrowing and shading lower limbs. Productivity and fruit color in the lower canopy declined when this shading occurs. The most vigorous limbs in the top must be pruned out to maintain adequate light penetration in the bottom of the canopy. Thinning cuts are preferable to heading or stubbing back cuts. Sometimes multi leader trees are created unintentionally by leaving too many permanent branches in the top of the canopy and letting these become too dominant. This condition can be corrected by removing two to three major limbs per year from the upper canopy over a three-year period. Dust converting the canopy back into a conical form, yields are reduced during this period of conversion so this technique is usually reserved for younger semi dwarf trees. Pruning and training techniques vary with varieties of different growth habits. Spurr type trees such as new delicious strains, tend to have fewer more upright scaffled limbs and more friuting spurs compared to non spur varieties. The limbs had minimal branching. In spur type apple blocks, a greater number of permanent scaffleds can be selected and strategic heading cuts are warranted when more shoot growth is needed.
Various training aids can be used to bend the limbs to more desirable orientation.
Terminal bearing trees such as Rome and Granny Smith tend to have weaving growth habits.
Hanging limbs are removed with thinning cuts or stubbing cuts. The spurs are short shoots and for good productivity should not be thinned too heavily, don't worry if terminal bearing trees do not look as pretty as trees of other growth types when you're done pruning. Young terminal bears and spur types both tend to a blind wood.
Delaying pruning until late spring will encourage more branching on blind shoots.
Bearing apple trees may be pruned once they have stopped growing for the season and after exposure to freezing temperatures. pruning in late spring and induces more bud break, pruning after bloom called the delayed dormant pruning is deenergizing and is a useful practice on trees that are overly vigorous.
Avoid pruning before a cold event, as pruning reduces the trees hardiness for about 10 days. The greatest loss of hardiness is within 48 hours of pruning, when the forecast indicates a potential drop to about negative twenty degrees Fahrenheit or drop of more than 50 degrees and inter negative numbers, stop pruning until the severe weather is past. Pruning is a cumulative process apple trees really have perfect forms and you do not want to remove every branch that is less than ideal. Prune only as much as needed consider, tree vigor, cropping, and natural growth habit. On large trees you can make about three big cuts and remove up to about a third of the smaller limbs.
It takes about three years to do corrective pruning on neglected trees. On narrow canopy trees such as the vertical axis you can make about one large cut per season, this should be a bevel or Dutch cut as described earlier for the purpose of lim renewal.
Although pruning is a dwarfing process, it isn't a substitute for natural size control and should be used as an aid not as a means of dwarfing.
Avoid severe pruning bend a limb rather than cut it out when possible.
Trees that are prune to heavily will have reduced cropping, excess wood production and will be less efficient. On trees that seem to need heavy pruning save some cuts for next year rather than sacrifice fruit yield.
Modern orchard planning should be pruned carefully to maximize cropping and fruit quality. Fortunately if you remember some basic pruning and training principles and techniques you'll make a huge difference in the success of an orchard operation. The main goal is to create windows to increase light distribution.
Use thinning cuts in most situations.
Reserve heading cuts for portions of the canopy were increased branching is desired.
Use a bevel or dutch cut for scaffold renewal where a limb has become overly vigorous. Ideal angles for permanent scaffold limbs are 50 to 75 degrees from vertical.
Pyramid shaped trees intercept the most sunlight maintain a tree structure that is wide at the base and narrow at the top. With the heaviest diameter branches in the first whirl and the branch diameter gradually decreasing in upper tiers. Avoid pruning before a cold event.
Avoid severe pruning.
Pruning is a cumulative process. Prune only as much as needed.
bending some limbs rather than removing them, save some cuts for next year. You will take tremendous pride in apple blocks you have handled in this manner.
As your impact on the orchard enterprise will be obvious. Apple trees will have better light quality, which will lead to higher productivity and better fruit quality.