LEAFLET NO: 404
Revised 9/93 - Author
LOW INVESTMENT PROPAGATION/WINTER PROTECTION
T.E. Bilderback, R.E. Bir & M.A. Powell
Extension Horticultural Specialists
North Carolina Cooperative Extension
North Carolina State University
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
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
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.
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
5. Repeat Step 4 using the remaining two (2) 2" x 8" x
10's. The two (2) bed sides (kickboards) are now
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
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
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
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
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.
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
race, color, national origin, sex, age, or disability. North
University at Raleigh, North Carolina A&T State University, U.S.
Agriculture, and local governments cooperating.