- -  AGRICULTURE CORE CURRICULUM - -


(CLF6000) Advanced Core Cluster: ORNAMENTAL HORTICULTURE

 (CLF6550)  Unit Title: PRUNING

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 (CLF6552)  Topic: TIMING OF         Time     Taught in Year(s) 
                     PRUNING           1 hour         3 and 4      
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        Topic Objectives: Upon completion of this lesson the student will 
        be able to:

        Learning Outcome #:

          (J-7) - Identify the appropriate time of the year for pruning 
                    and discuss why the time of pruning is important.

        Special Materials and Equipment: 

        References: Editors of Ortho Books. (1989). ALL ABOUT PRUNING. 
                      Available from: Ortho Books, P.O. Box 5047, 
                      San Ramon, CA 94583.
                    Editors of Sunset Books and Sunset Magazine. (1990).
                      WESTERN GARDEN BOOK. Menlo Park, CA: Lane Publishing 
                      Co.
                    Harris, Richard W. (1983). ARBORICULTURE: CARE OF 
                      TREES, SHRUBS, AND VINES IN THE LANDSCAPE. Englewood 
                      Cliffs, NJ: Prentice-Hall.

        Evaluation: Quiz by instructor

TOPIC PRESENTATION: TIMING OF PRUNING

A. The appropriate time to prune depends on the type of plant, its 
   condition, and the results desired.

   1. In general, the best time to prune a woody plant is late winter or 
       early spring, the period just before new growth starts.

       a. At this time, there is the least loss of the plant's stored food 
           reserves (sugars) and pruning cuts heal more quickly.

       b. Also, at this time when the leaves are gone on deciduous trees
           and shrubs, it is easy to see the structural arrangement of the 
           branches and plan pruning strategies.

       c. Removal of mistletoe is easiest during the dormant season; the 
           green mistletoe is easily seen growing on the bare branches.
   2. Pruning in fall or early winter should generally be avoided.

       a. Before the foliage drops, the plant's stored food reserves move 
           from the leaves into the woody branches; pruning at this time 
           depletes the stored food reserves needed to initiate spring 
           growth.

       b. Also, fall is when many decay fungi produce spores, so this is 
           when open pruning wounds are most likely to become infected with 
           decay rot.

   3. In most cases, the worst time to prune is just after leaves emerge
       in the spring.

       a. Stored energy has made the sprouting and growth of new foliage 
           possible, but the leaves have not yet begun to accumulate food 
           to replenish the supply.

       b. Spring is the time of greatest root growth which also uses a lot 
           of the plant's stored energy.

       c. A plant can ill afford to lose foliage until food manufacture 
           equals or surpasses food utilization.

       d. Additionally, in spring the tissue beneath the bark is soft and 
           can be easily damaged during pruning.

   4. Pruning during the period of spring to midsummer has a dwarfing 
       effect on plants because this reduces the leaf area for the longest 
       time.

       a. Bonsai plants--where dwarfing is the goal--should be pruned at 
           this time.

       b. Summer pruning is recommended for restricting the growth of 
           ornamental plants that have reached a desired height and spread,
           such as established evergreen shrubs and hedges.

       c. Summer pruning cuts should be kept small because the wounds will 
           not callus over as rapidly as during the late dormant season.

   5. Some pruning can be done at any time IF judgment and moderation are 
       exercised.

       a. Dead and dying branches, suckers, and water sprouts should be 
           removed whenever they are seen.

       b. Removing a few stragglers or branches that are out of line does 
           little harm, even if it is done during the growing season.

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       ACTIVITY:

       Have students prune half of an established evergreen hedge in
       January, and the other half in May or June. Have them compare:

         1) additional pruning required
         2) appearance of the hedge
         3) growth responses
         
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1/11/91 CLH/clh

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