The first week of December is at a close and nighttime lows are approaching freezing temperatures. We’ve spent the last week installing Greenhouses, known as Caterpillar Tunnels or Low Tunnels, and our plants will now enjoy a boost of warmth from the added heat units and those little leaves will begin to grow faster than they would in natural winter temperatures. For example, today was a 60°F, but inside the Greenhouse it reached 90°F before the vents were open at noon.How’d we do that?
We started with the skeleton of the greenhouse. We pounded 2ft long rebar, with 1ft into the ground, and spaced them every six feet. Next, PVC pipe arches were placed over the rebar and secured to the bed with U shaped brackets. To calculate how log the arches of PVC needed to be, we used the equation d(3.14)/2. The “d” stands for diameter, for which we measured the width of the garden bed (the bed pictured above is thirteen feet wide and we treated that width like the diameter of a circle). Then, we found the Circumference of a circle (d(3.14)) with a diameter of 13ft which equals about 40ft. We divided 40 by 2 and got 20ft for the length needed for our half circle PVC arches. A ridge pole, or the spine of the greenhouse, was fashioned with furring strips on our larger greenhouse, we used rope for the ridge poles on our smaller low tunnels. Six millimeter thick greenhouse plastic was stretched over the hoops and attached to the garden bed with furring strips and screws. Clamps are used on the ends to secure the plastic and vent the greenhouses.