LEAFLET NO: 404
Revised 9/93 - Author Reviewed 4/96

LOW INVESTMENT PROPAGATION/WINTER PROTECTION STRUCTURE

T.E. Bilderback, R.E. Bir & M.A. Powell
Extension Horticultural Specialists
Department of Horticultural Science
North Carolina Cooperative Extension Service
North Carolina State University

Basic Structure:
     Quonset Design
          3' High x 6' Wide x 20' Long
          3/4" schedule 40 PVC pipe bows slipped into 3/4"
               electrical conduit hangers
          6 ml white copolymer cover
          2" x 8" treated lumber kickboards along sides and ends


List of Structural Materials and Approximate Costs (1993):

      Quantity               Description                    Cost 

          4         3/4" PVC pipe, 20' lengths             $10.40
          1         12' x 30' white copolymer film, 6 mil   12.60
          32        3/4" electrical conduit hangers          6.08
          1         2" x 8" x 12' treated lumber            10.96
          4         2" x 8" x 10' treated lumber            36.52
          1 lb      16 penny common nails                    0.87
          1         200 ft. roll guage steel wire            4.38
          1 lb      roofing nails                             .87
          4         metal 4"x5" mending plates (4 x4.5)      1.80
                                                Total       84.48


Tools Required for Construction:

     Carpenter saw                          Garden rake
     Carpenter hammer                       Side cutting pliers
     Folding rule or tape measure           Sharp pocket knife
     Round pointed shovel                   Builder's square
     Pencil
Site Selection:  Choose a site for your structure that is fairly
level and preferably has some shade.  If the structure is to be
used exclusively for propagation, it should be oriented east-
west.  If its primary use will be in providing winter protection
for nursery crops, it should be oriented north-south.  There
should be a water source nearby since water is needed for both
propagation and winter protection.


Construction:

      1.     Level an area (properly oriented depending upon
             whether your structure will be used for propagation 
             or winter protection) 8' wide x 24' long.

      2.     Square ends of lumber.

      3.     Cut the 2" x 8" x 12' in half so that you have two  
             (2) pieces 2" x 8" x 6'.  These 6' sections will    
             be used for the ends of the bed.

      4.     Butt the ends of two (2) of the 2" x 8" x 10's
             together and nail securely so that you have a 2" x  
             8" x 20' using splice connectors on each side of the
             splice.

      5.     Repeat Step 4 using the remaining two (2) 2" x 8" x
             10's.  The two (2) bed sides (kickboards) are now
             assembled.

      6.     Lay kickboard sides on edge 6' apart on the levelled
             area and place 2" x 8" x 6' section outside each    
             end.  Be certain that corners are square, then nail 
             together securely.  You now have a rectangular box  
             with open top and bottom that has inside dimensions 
             of 5'8 3/4" x 20'.

      7.     At each of the four (4) corners along the length of
             the structure (on the inside edge) nail in a conduit
             connector so that the top of the connector is flush
             with the top edge of the 2" x 8".  Any nails which  
             come through should be bent over so that they will  
             not tear the copolymer cover.

      8.     Repeat Step 7 but with the bottom of the connector
             flush with the bottom of the 2" x 8".

      9.     Starting from the center of either of the top end
             conduit hangers mark off the kickboards along the
             length of the structure at 33 13/16 inch intervals.

     10.     At each of the marked intervals nail in two (2)
             conduit hangers as in Steps 7 and 8.

     11.     Cut the four (4) 20' lengths of PVC pipe in half so
             that you have eight (8) 10' pieces.

     12.     For each section of PVC pipe, slip one end down
             through a set of conduit hangers, bend the pipe in a
             bow across the width of the structure and slip the
             other end of the pipe down through the opposite set 
             of conduit hangers.

     13.     Install remaining 3/4" PVC bows as in Step 12.

     14a.    If the structure is going to be used for winter
             protection of containerized plants follow Steps 15  
             and 16, then Steps 19-22.

     14b.    If the structure is going to be used for propagation
             of cuttings follow Steps 17 and 18, then Steps      
             19-22.

     15.     Place containerized materials inside the structure. 
             More cold tolerant plants such as creeping junipers
             should be placed around the perimeter.

     16.     Water all containers thoroughly, then follow Steps  
             19-22.  Preemergent herbicides should have been     
             applied 1 month earlier.  Apply fungicides after    
             irrigation.  Rodent bait should be applied just     
             before covering.

     17.     Fill the structure to a depth of 6" of 7" with      
             clean, moist propagating medium.  Be certain that   
             medium is level.  An alternative to filling the     
             frame is use of cellular trays.

     18.     Insert cuttings and water in thoroughly; then follow
             Steps 19-22.

     19.     Using flexible wire or heavy cord tie the bows.     
             together so that they cannot flex to either side.   
             Another alternative is to use a single PVC 20"      
             length centered at the top and attached to each bow 
             to add greater rigidity to the frame.

     20.     Center the 12' x 30' sheet of white copolymer film
             over the hoop frame

     21.     The cover can be secured by covering the 1' of      
             surplus film along one of the long sides with soil. 
             To allow easy access to the plants or cuttings the  
             other three sides of the film can be held down with 
             boards, rocks or pieces of wood.  Winter protection 
             structures should have kickboards braced with soil  
             or gravel during snow season to provide extra       
             support. 

     22.     On warm days your structure may require venting.    
             This can be done by opening the ends and then       
             closing them down again later in the day.


If properly constructed the framework of your quonset should last
for years.  With a minimum amount of care the white copolymer
cover should last for two (2) years.  Precautions should be taken
to insure that nails and wire used in construction of the
framework are properly bent and do not tear the cover.  Also, if
the structure is not going to be used for prolonged periods, it
is best to remove the white copolymer cover, carefully roll it up
and store it out of direct sunlight.  Do not fold the cover as
the creases will cause weak areas which will tear easily when the
cover is replaced on the quonset!  Storage of the cover, when not
in use, will extend the life of the white copolymer.

                          Published by
          North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.