Plastic Tunnel Cold Frames

     Sadly, the summer growing season is coming to an end.  It may seem a little crazy to be talking about cold frames on one of the hottest days of the summer, but now is the time to start planning for colder weather.  One of the easiest ways to continue gardening well into winter is to build a cold frame.  Here are some tips for an easy to build plastic tunnel cold frame.

     In contrast to traditional cold frame design, this design is easy to set up in the fall and also store during the summer.  It consists of ribs made from polyethylene water pipe, plastic sheeting, and some wood.  It can easily be made for less than $50.

  • 5 – 5 ft. lengths of ¾ in. polyethylene water pipe
  • 10 – ½ in. x ½ in. x 14 in. wooden stakes (or rebar for better strength)
  • 1 – 12 ft. x 6 ft. 4 mil clear plastic sheet (used for construction)
  • 4 – ½ in. x 1 in. x 8 ft. wood strips

How to Build It
     The first step is to cut the parts to size.  For this project, black polyethylene water piping that comes off of a spool works great as it already has the bend that we’re looking for. 
     After cutting everything to size, the second item to tackle is the plastic sheet.  Fasten the poles to each long edge of the plastic sheet.  I used staples to do this, and then rolled the plastic around one piece of wood and fastened another strip to it so that the plastic is sandwiched between the wood.  This makes the edges durable and also helps weight down the edges to protect against winds.
     Finally, drive the stakes into the ground where you want them, and slip the piping over them to create ribs.  Then it is just a matter of covering the ribs with the plastic sheet to finish off the cold frame tunnel.  If you’re in an area that tends to be windy, you may want to add some bricks to help weigh down the plastic.

     Seeds germinate fast when the soil is already nice and warm. For delicious, picture-perfect fall crops of spinach, lettuce, peas, kale and broccoli, now's the time to plant.  Plants that thrive in fall weather include: carrots, beets, broccoli, Swiss chard, kale and all kinds of salad and Asian greens. Choose disease-resistant varieties that mature quickly. All can be direct sown into the garden, though broccoli can also be started indoors under lights or in a greenhouse. With these crops and a cold frame it is possible to enjoy fresh salads all year!