- -   AGRICULTURE CORE CURRICULUM  - -


(CLF7000)  Advanced Core Cluster:  PLANT AND SOIL SCIENCE

  (CLF7600)   Unit Title:  PRUNING

____________________________________________________________________________
  (CLF7605)   Topic:  TIME OF          Time      Taught in Year(s) 
                      PRUNING         1 hour           3 and 4       
____________________________________________________________________________

         Topic Objectives:  Upon completion of this lesson the student will 
         be able to:

         Learning Outcome #:

           (K-10)  -  Identify the appropriate time for pruning both trees 
                      and vines and discuss why the time of pruning is 
                      important.

         Special Materials and Equipment: None

         References: University of California,.  PRUNING GRAPEVINES.
                       Cir. 477.

                     University of California,.  PRUNING LANDSCAPE TREES.
                       AX7 288 or Leaflet 2574.

         Evaluation: Quiz by instructor

TOPIC PRESENTATION:  TIME OF PRUNING

A.  The timing and severity of pruning are important in the development and 
    productivity of fruit trees.  Best results are usually obtained when 
    pruning is done during the dormant season.

B.  Most pruning in California is done after leaves fall and before new 
    growth appears in the spring.  (Late November through early March.)

C.  At the end of any growing season the top and root system of a tree will 
    be in balance.

    1.  The root system is extensive enough to supply the top.

    2.  The above ground parts are sufficient to manufacture the food 
        necessary for future development of the whole plant.

D.  Cutting back the top will result in each remaining bud having a larger 
    proportionate share of the available moisture and nutrients, and 
    subsequent growth will be more vigorous.

E.  Any pruning reduces, in proportion to its severity, stored food and 
    potential leaf area.

    1.  Heavy pruning on a young nonbearing tree is dwarfing.

    2.  Heavy pruning on a bearing tree may result in increased vigor.

    3.  It is much easier to see what you are doing when there are no leaves 
        on the tree.

F.  Pruning is most invigorating when done in the dormant season but there 
    are other factors to consider. 

    1.  Winter rains and winds spread several diseases.

        a.  When fresh wounds (pruning cuts) are made during inclement 
            weather fungus spores and bacteria can be transmitted by 
            the wind or rain.

        b.  Cytosporina of apricots is known to enter tree wounds at this 
            time.  Possibly bacterial canker, also, enters the tree this 
            way.

    2.  Some plants like walnuts and grapes will "bleed" quite profusely 
        when cut (pruned) late in the season.

        a.  Alternating warm days and cold nights apparently encourage this 
            effect.

        b.  "Bleeding"  is usually not harmful to the tree, but if it is 
            heavy and persistent, it could cause bark injury below the cut.

        c.  If the tree is being cut for grafting, bleeding can be a real
            problem.  Any type of grafting compound used is floated or 
            lifted by the exuding sap.

    3.  Dead branches are usually easier to find when trees are pruned late.

    4.  Very late pruning of grapevines does have one advantage.

        a.  By delaying pruning until the upper buds on canes have grown an 
            inch or two, one can retard the starting on the lower buds 
            (those on the spurs) for a week to 10 days.

        b.  Frost damage is avoided if frost occurs during these first few 
            days of growth.

        c.  In specific areas of Southern California and the central coast 
            increased yields have resulted when vines are pruned late.
            Reasons for this are not fully understood.


7/25/90 sg

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