- -  AGRICULTURE CORE CURRICULUM - -


(CLF6000) Advanced Core Cluster: ORNAMENTAL HORTICULTURE

 (CLF6550)  Unit Title: PRUNING

____________________________________________________________________________
 (CLF6551)  Topic: PURPOSES OF         Time     Taught in Year(s) 
                     PRUNING             1 hour      3 or 4
____________________________________________________________________________

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

        Learning Outcome #:

          (J-1) - Discuss why pruning is necessary for healthy plant
                    growth.

        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: PURPOSES OF PRUNING

A. Control Size

   1. Plants in landscape settings are usually part of an overall 
       landscape design and they need to be pruned regularly to preserve 
       the integrity and scale of this design.

   2. Plants in landscape settings frequently need pruning to prevent
       their poking the side of the house, resting on the roof, obscuring 
       windows, growing over walkways and driveways, and generally posing a
       danger overhead.

   3. Other size factors that must be considered in landscape settings--as 
       opposed to natural woodland settings--are interference with utility 
       wires, the danger of wind-throw, ease of pest-control spraying, and 
       blockage of light to other landscape plants or lawn areas.
   4. If a plant requires constant, heavy pruning to control its size, it 
       is probably the wrong plant for its location and use. Homeowners 
       all too frequently plant trees and shrubs too close to each other, 
       too near the house, or in a location where their ultimate size is 
       unacceptable.

B. Control Shape

   1. The particular pruning techniques chosen determine whether the plant
       retains its natural shape or takes on a formal shape. Examples of
       formal shapes are:

       a. Bonsai - intentional dwarfing

       b. Topiary - pruning into specific shapes, such as geometric forms
           or animal outlines

       c. Espalier - training plants to grow flat by means of a trellis,
           wires, hooks, or supports; the plant can be either free-standing 
           or against a wall

       d. Pleaching - weaving together or intertwining the upper branches
           of several trees

       e. Pollarding - heading back one- or two-year-old branches to 
           approximately the same place year after year

   2. Most often, pruning is done to help a plant retain its natural shape
       by removing wayward, uncharacteristic branches.

   3. Controlling the shape of pruned plants also entails controlling
       their size, which, for the reasons given above, is especially 
       important in landscape settings.

C. Increase Vigor

   1. Annual pruning encourages old growth to give way to new wood, which 
       flowers more profusely and is more resistant to disease and insects.

   2. Removing selected branches also allows the sun and air to penetrate
       the interior of the plant. When exposed to sun, foliage expands to
       its fullest.

D. Direct Growth

   1. Undesirable branches can be removed by pruning; likewise, growth can
       be encouraged where foliage and branches are wanted.

   2. Plants can be pruned to fulfill a particular function, such as a 
       climbing tree for children or the creation of a shady grove.

E. Protect Investment

   1. Mature, well-kept landscape plants make residential property more 
       valuable.

   2. Regular pruning protects the initial investment made in landscape 
       plants and landscape designs.

   3. Regular pruning reduces the likelihood of damage by diseases and 
       pests, neglect, or too much shade killing a lawn.

F. Control Damage and Disease

   1. Severe winds can break or damage even properly pruned trees and 
       shrubs. Pruning can help redirect growth in a desirable manner.

   2. Proper pruning can prevent the total loss of storm-damaged plants.

   3. Removing diseased or infested portions of a plant can slow or stop
       the spread of the disease or infestation (for example, mistletoe).

G. Public Safety

   1. Tree branches that pose a hazard (for example, structurally unsound,
       too low) to pedestrians, cars, and structures should be removed 
       before they cause injury or damage.

   2. Sightlines (for example, at street intersections) can be maintained
       by pruning.

   3. Trees and shrubs in public parks are increasingly being pruned 
       specifically to reduce cover for attackers.





1/14/91 CLH/clh

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