High Elevation Gardening Web Log "Blog"

We used twenty-five large cinderblocks to line the perimeter of our 4’ x 8’ area. We placed the hole sides up and down and then dug up the dirt inside the framework. We removed the larger rocks and hauled in several buckets of ground glass or “sand” from the recycling center on Butler Ave. We screened the “sand” to remove the larger pieces of glass and mixed the sand with enough compost to cover the area with about 1 inch of the mixture. We used approximately a 1:3 ratio of sand to compost. (My concern about the recycled glass injuring the earthworms proved unnecessary.) Where we planted the radish and carrot seeds, I dug the mixture in with a small hand shovel and removed as many small rocks as possible.

At either end of the two 8-foot long rows of cinderblocks, we inserted into corresponding holes the ends of a 10-foot piece of ½” CPVC plastic water pipe. We repeated this process about every 16” and used a total of six lengths. This process creates an upside-down U-shaped framework that resembles a Quonset hut. We placed rocks or dirt into holes of the blocks to secure the framework then we tied another 10’ length of pipe under the top of each upside-down U to stabilize the structure. (You can include a sprinkling system here if you want.) Over this framework we placed a 10’x 20’ sheet of plastic, which we cut to the appropriate length. Just remember to take into account the height of the structure when you calculate the length—too long works better than too short.

Securing the plastic sheet under the block is necessary. However, the challenge comes in finding a way to secure the plastic sheet and still access the inside of your “greenhouse.” You can secure one or more sides under the blocks and use rocks, wood, or dirt to secure the others. Located near the south side of my house and under the deck, my garden is protected from the wind and gets lots of winter sunshine. During midday, I often open one end just to cool the temperature down inside. However, one must avoid doing so on windy days.

The plastic holds in moisture and aids the germination process. When the inside temperature rises, moisture will collect on the plastic. As the temperature cools it will begin to “rain” inside. Even with the low amount of precipitation we had last winter, my two rain barrels provided enough water for the garden until the first spring rains came. I am definitely looking forward to the cool days of fall and harvesting fresh greens from my garden all winter long. Today, my kale and broccoli seedlings are on the windowsill, my chard is ready to harvest in the garden, and my lettuce is coming up.

By Rebecca Snow
The author is a Master Gardener volunteer for Coconino County Cooperative Extension. Do you have a gardening question? Call the Master Gardener hotline at 774-1868 ext. 19. For more information on gardening classes and gardening events, visit the Master Gardener web blog at highelevationgardening.arizona.edu.