1) Using your tin snips or box knife, cut the polycarbonate panel into 2-foot lengths.
Cut the panel into segments
2) Drill (or punch with a nail) a whole in the top, center and bottom edges of each panel.
Drill (or punch) holes in the panel in the following locations
3) Cut the coat hanger as shown. This should give you a wire about 18-inches long with a hook at either end.
Cut the coat hanger with wire cutters as shown
4) Find the center of your wire, and bend it about 6-inches on either side. This will allow you to make the hoop taller or wider based on your needs.
Bend the wire upward 6-inched from the center
5) Curve the panel and pass the wire through the holes in the center on either side.
Pass the wire through either side to create a half-dome
The mini greenhouse assembled
The extra holes at the ends of the panel can be used to secure it to the ground with fabric pins, or to join two panels together to make a longer tunnel.
The mini greenhouse in a garden bed.
Note these panels absorb a lot of heat, so if you join multiple panels together, the air circulation will be reduced and the middle will be much warmer (20° or more) than the edges.
As you can see from my own tests, these little greenhouses are very good at capturing heat, and will add 10 or more degrees to your soil in a matter of minutes.
Temperature before the greenhouse
The temperature 10 minutes after the greenhouse is in place
I tested one all day, and it averaged about 25 degrees warmer than the air, and trapped enough heat in the soil so that it never fell below 40 degrees at night, even when the surrounding area fell to 32 degrees.
My garden is on a west-facing slope, so it’s shaded for several hours longer in the morning than the nursery, so I still need to wait a couple more weeks before I put anything into the ground.
But I am looking forward to these little greenhouses helping me get started outdoors four to six weeks than I would be able to otherwise!
Have you built a similar mini-greenhouse for your garden? Tell me about it in the comments below so I can share it with others!