- -   AGRICULTURE CORE CURRICULUM  - -


(CLF7000)  Advanced Core Cluster:  PLANT AND SOIL SCIENCE

  (CLF7600)   Unit Title:  PRUNING

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  (CLF7604)   Topic:  PRUNING         Time      Taught in Year(s) 
                      SYSTEMS         1 hour          3 and 4       
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         Topic Objectives:  Upon completion of this lesson the student will 
         be able to:

         Learning Outcome #:

           (K-2)  -  Prun, open center, modified central leader, and 
                     central leader type trees.

           (K-3)  -  Explain the difference between the three major types of 
                     tree pruning systems.

           (K-4)  -  Discuss the purposes of training trees to one of 
                     the three systems.

           (K-14)  - Prune small fruit trees grown locally.

         Special Materials and Equipment: Pruning shears, sharpening stones 
                     and light oil.

         References: University of California,.  (Leaflet 2471).  TRAINING 
                       YOUNG WALNUT TREES.  Modified Central - Leader 
                       system.

                     University of California,.  (Leaflet 2252).  TRAINING 
                       AND PRUNING FRUIT TREES AROUND THE HOME.

                     University of California,.  (Leaflet 2759).  CARE OF 
                       FRUIT TREES IN THE HOME ORCHARD.

                     Stebbins, Robert L.,  (1980).  TRAINING AND PRUNING 
                       APPLE AND PEAR TREES.  Pacific Northwest Extension 
                       Publication.  (PNW156).

         Evaluation: Quiz by instructor

TOPIC PRESENTATION:  PRUNING SYSTEMS


A.  The shape of a tree and the selection of its framework branches are 
    determined by training systems used on the young tree.  Training systems
    are chosen for each tree type according to the natural growth habit of 
    the tree, management and harvesting requirments of the crop and the 
    growers own preferences.

B.  We will discuss each of the three commonly used pruning systems 
    individually.

    1.  The central leader type of tree is often used for apple trees.

        a.  Here the tree is pruned so that the main shoot predominates.

        b.  As time passes the tree becomes pyramid in shape (like a 
            Christmas tree).

        c.  Often the lower branches become shaded by the upper ones.

        d.  This system is not often used.

    2.  The modified leader type of a tree guarantees a mechanically strong 
        framework and is often used for walnuts.

        a.  The tree is pruned to a single leader tree for 2 to 3 years, 
            then the leader is cut and lateral branches are selected for
            development into major scaffold branches. 

        b.  The result is a development of usually four to six well spaced 
            scaffolds with strong crotches. 

        c.  The canopy of these trees have a spherical shape.

        d.  Pecans, walnuts and some varieties of apples lend themselves to 
            this system.

    3.  The open center (vase) system is most commonly used in California 
        for Prunus species such as peach, plum, apricot, and almond.

        a.  Properly used this system has proved very satisfactory because 
            of excellent sunlight distribution and accessability to 
            ladderwork.

        b.  Three or four primary scaffolds branches are selected after the 
            first years growth in the field.

        c.  Definite care needs to be taken so that not all branches 
            (scaffolds) will arise at the same point on the trunk.  Basin 
            crotches (water pockets) may also result when 3 branches arise 
            at the same point.

        d.  The centers are kept open, but still full enough to prevent 
            sunburn of branches. 

        e.  The amount of openness varies with the species, variety and the 
            growers personal preference.


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          ACTIVITY:  
                      
          1.  Prune open center, modified leader, and leader type
              trees.  A good approach is to demonstrate the proper
              pruning techniques for each type of pruning system,
              then let each pair of students prune a single tree 
              (only 1 pruning shear to be used on one tree at a 
              time), then let each student prune several trees 
              individually.

          2.  Pruned branches from larger trees will make good 
              practice (young trees) for beginning pruners.
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7/25/90 sg
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