Mini-Greenhouse: Protecting Winter Greens in our Desert Garden

Learn how we built our angled mini-greenhouse with scrap PVC.

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by AdobeStock/caftor

Winter is coming on here at our Arizona desert homestead and, even though the temperatures are dropping, we still look forward to eating fresh kale, chard, escarole, lettuce, and other fresh hardy produce all winter long with the aid of a mini-hoop house. Don’t be misled by the fact that our homestead is in the southeastern Arizona desert. Last year, one storm dropped six inches of snow on our place. The following week, another cold front brought our temperatures here at the Bear Cave down to 2°F here at our 5,000 ft elevation. Down in the valley, it was below zero. It certainly gets cold enough here to zap most tender growing garden plants without some protection.

row of plants in a garden with a white plastic sheet laying on the ground next to it

Last year, we simply protected as well as we could with row cover. We found that without supports, heavy frost and snow broke down some of the plants under the row cover. While it probably didn’t hurt the nutritional value when we used them immediately, we really felt sad about the squashed greens. They looked pretty pathetic.

white pvc pipe leaning up against a blue wheelbarrow

So this year, we decided to give them another layer of protection. Our neighbor had done some plumbing in a new out-building and had left a small pile of scrap 3/4″ PVC out behind his shop. Our Arizona sun had baked the pieces for a number of months and they were definitely too brittle to make a hoop. Enter the PVC angled joints. With a few PVC fittings, a pair of 45 degrees and one 90 degrees, we had our own version of a hoop for our mini-greenhouse. By repeating this five times, we had the supports for our mini-greenhouse.

drawing on grid paper showing the angles for a mini greenhouse plan

Barbara, our resident math expert (among so many other things), drew out a plan using the width of our raised bed as the length of the hypotenuse of the isosceles triangle that was then used to calculate the length of the top or diagonal  sections of our “hoop”. In the above drawing, the diagonals were cut at 31″.

PVC cuts laid out

This calculation gave me a very accurate measurement for the length of the angled “hoop” sections. This resulted in the top sections of PVC being cut to 31″ based on the 43″ outside width of the raised bed. We determined the rise of the “hoop” by estimating the height of the greens at the edge of the raised bed. In our case, we made the side pieces 14″ high.

row of plants with triangular hoops spaced out above them

We assembled five of these hoops to give us a mini-greenhouse with supports every 2-1/2′. We dry-fit the joints for convenient disassembly and storage next summer.

pvc pipe over top of rebar

We drove pieces of rebar into the ground at the outer edge of the bed and slipped the end of the PVC hoop over it. We then tied the PVC hoop to the raised bed with plumbers tape and a couple short sheet rock screws. Besides allowing us to level the tops, this seems to support the hoops well enough to handle both the weight of the plastic cover and the persistent wind we have here.

plastic sheet tied to pvc pipe

We cut off a section of 10′ wide 6 mil plastic long enough to enclose the ends of the structure. The fold in the plastic at the center made it easy to mark and reinforce the tie-off spots with 10 mil PVC tape that we had left over from running our propane line from the tank to the house. We punched two sets of holes in the tape and plastic to create a make-do grommet.

row of plants with pvc hoops above them and a plastic sheet rolled up on top

Two sections of light cotton line tied with the ends out on one side and in on the other made a system that allows us to tie up either one side or both sides for picking produce or working in the garden.

row of plants underneath a mini greenhouse made of pvc pipe and plastic sheeting

On the coldest nights, we raise one side of the plastic and lay in row cover directly on the tops of the plant and roll down and anchor the plastic on both sides.  With the plastic shelter above, we don’t worry about frost, snow, or heavy rain on the row cover flattening our greens. The double layer is a bit like putting a down comforter on the bed on a cold night.

turkey soup in a black bowl

This is a picture of the payoff. Yesterday, Barbara opened the mini-greenhouse and picked a few carrots and some chard to put in our turkey and dumplings. What a great finale to a Thanksgiving turkey feed and a great reward for the work of building our little hoop house.

We are constantly looking for ways to improve the way we build and garden.  Many of you have offered great suggestions. We hope some of you will benefit by the mini-greenhouse plans we have shared.

Find more resources for greenhouse building by visiting structures and outbuildings.