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Bear Cave Mini-Greenhouse: Protecting Winter Greens in our Desert Garden

Dave L HeadshotWinter 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 2⁰ 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.

Garden Bed w Row Cover


 

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.

Scrap PVC
 

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 45⁰ and one 90⁰, 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.

Formula for Triangle Sides
 

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".

Hoop Sections
 

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.

Hoops
 

We assembled five of these hoops to give us a mini-greenhouse with supports every 2 ½’. We dry-fit the joints for convenient dis-assembly and storage next summer

Connectors
 

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. 

Fastening Hoop House Plastic
 

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.

Hoop House with Tied Sides
 

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.

Hoop House
 

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 and Dumplings
 

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. We invite you to visit us at www.grow-cook-eat-beans.com for more about our desert homestead experience.

 

dave larson
12/12/2011 12:15:06 PM

Hi N Dave, Have to say that I don't miss those freezing rains turning to snow. Grew up in Minnesota, then Alaska, Colorado and Oregon and experienced a bunch of bad driving days. Hope your daughter stays safe. We do, however, get snow here as well as some pretty good rains. We have had one or two 6" snowfalls per year and quite a few in the one to two inch category. Nothing like Nebraska, however. Our 4,600 ft elevation makes our little snow shedding hoop house a snug shelter for the greens. We have fresh lettuce and escarole for salads every day and our kale and chard are doing very well. We'll keep you posted as the winter passes. Have a great day in Nebraska!


dave larson
12/12/2011 11:50:08 AM

Hi Roxane, thanks for visiting and commenting on the blog. Sorry it's taken a bit to get back to you. We have been visiting grandkids. On the ends of the frame, we change from open to closed on pretty much a daily basis and even, when it's really cold, put the row cover directly on the plants and then seal the system. We simply cut the plastic long enough to reach the ground or edge of the raised bed and then make a tuck on each side - just like wrapping a gift. Then we simply weight it down with a left-over chunk of 4" x 4" or a rock. Works pretty well even though it doesn't look "professional" - It is easy to access and easy to vent. Hope this helps. Love to see some pics of your place in Tennessee. Have a great day.


roxane whisnant
12/9/2011 9:28:53 PM

Thank you Dave!I need your help! Ihave had (in my pea brain) what you have so explained here in great detail. Seeing the steps makes it so workable for us here. We're in middle Tennessee and had our first snow-ball fight two days ago (our 2nd snow thus far). We're looking at 19 degree temps tomorrow night and I'm heading out to Lowe's for some rebar tomorrow and dry fitting this over my fall veggie garden. My fall veggies got planted later than ever, Sept./Oct. was a blurr with the birth of our 3rd grandchild. I got everything planted, but have been using straw/hay and old sheets to provide shelter during the nighttime dips. We have a salad mix, onions, spinich, beets, brussels sprouts, red cabbage, green cabbage(s), and brocolli rabe. There just isn't anything in that lineup I want to lose. One HUGE question though. How do you prepare the ends of your bed covers? Do you allow for the height in the length of the row coverage? Just want to get it done right. And, give a personal thank you to your mathematician! Thanks so much.


nebraska dave
12/2/2011 6:32:13 PM

Dave, great way to cover your plants for the cold months. We are getting close to single digit coldness here. The temperature was 11 degrees this morning. Thank goodness the wind was not blowing like the two days before. I haven't really ever tried to protect a fall crop with cover. I don't know how much snow you get there but your cover looks like it could hold up a good load that's for sure. The weather reporters are predicting rain turning to freezing rain and then 3 to 6 inches of snow for tomorrow. I don't really like that freezing rain and then turning to snow stuff. I don't mind rain and I don't mind snow but freezing rain with snow on top makes for some mighty slippery streets. I don't have to get out in it but my daughter does. You will have to keep us updated on how the greens do over the cold winter days. Have a great late fall day in the garden.