Sage Gardens

In an earlier post I wrote that I was going to re-cover my coldframe greenhouse. And despite a few days delay due to bad weather, I did finally get around to it.

About 10 years ago when I built the greenhouse, I had originally looked into getting a nice glass one, but I didn’t have the $7,000 to $10,000 to spend, so I had to look into cheaper alternatives.

I happen to live in a big flower and indoor plant growing region of the country, with large growers like Kent’s Bromeliads and Plug Connection and hundreds of smaller outfits all within a couple mile radius. Most of these operations (large and small) use aluminum-framed round-top greenhouses covered with and extra thick and flexible plastic designed specifically for this use. Since we have lots of sunny days, and temperatures rarely dip below the freezing mark, these types of greenhouses work very well here. They trap enough heat to keep the plants warmer than they would be outside, but they also release it easily enough so you don’t have to have a lot of cooling and ventilation systems beyond a couple of openings at either end (and maybe one or two on top).

After visiting a friend’s growing operation (he grows poinsettias), and reading a few books on building greenhouses and greenhouse basics, I figured I knew enough to build my own from scratch.

Rather than using aluminum or wood framing, I decided to build mine with schedule 40 PVC pipe and cover it with 6mil plastic. PVC is lighter, less expensive and easier to work with than aluminum, and it won’t rot like wood. I was able to get all the components I needed to build a 10′ by 18′ greenhouse from my local home center for about $150–much better than $7,000! (One day, I’ll get around to posting the plans here on the site so you can build your own.)

The only drawback is that after a full season of sun exposure, 6 mil plastic tends to crack and split. You can extend the life of the plastic by 6 to 8 weeks by spray painting it with white paint, but I usually don’t go to the effort. I use my greenhouse primarily in the late winter/early spring to get plants started, and again in the fall to extend the season a bit, so I don’t really need it covered 365 days a year.

Anyway, toward the end of winter each year I go though the process of re-covering the greenhouse and getting it prepped for the new growing season. Here’s how this year’s went:

Step 1: Cleaning it up

After standing uncovered all winter and having the chickens, ducks and other animals in the lower yard trampling through it, the greenhouse is a real mess. All of the tables, pots, buckets, etc. have to be removed. Before the new covering can be placed on it, the frame has to be scraped with a putty knife to remove the old plastic and glue.

The tools

My tools — a roll of 6 mil plastic, a glue gun and low-temperature glue sticks. It’s quick, inexpensive and does a great job of secureing the cover to the frame.

Setp 2: The back wall

Starting with the back wall, which is on the low part of the hill facing west, I use a spring clamp to hold the plastic in place as I glue. Istart at the top and work my way halfway down one side, then go back to the top and work halfway down the other.

Finally I glue all the way down to the base on both sides, tuck the bottom of the plastic under the frame base and glue it in place. Then I go back and trim the excess from the sides, making a complete wall.

Step 3: The front

I do the front in two segments because there’s less wasted plastic with the door and vent window in the center.

As with the back wall, I clamp and glue one side, snipping the plastic and gluing around the door frame.

Then I repeat on the other side to complete the front. Finally, I’ll snip the plastic around the upper vent and glue it to the vent frame.

Step 4: The top

Getting the plastic over the top of the greenhouse is the hardest part to do working alone. I unroll about 25 feet of the plastic, cut it and then pull it over the top of the greenhouse while it’s still folded. Once I’ve got it pulled over and evened out on both sides, I unfold it on one end and open it a far as it will go. Then I switch to the other side and do the same.

Eventually it unfolds enough where I can drag one end all the way to the front and the other all the way to the back. Then I just have to even out the ends so it hangs over the front and back equally.

Step 5: attaching the top

Once I’ve got the overhang equal, I clamp the plastic in place and glue the top to the frame the same way I do the ends. The excess is trimmed from the front and back while excess on the sides is tucked under the frame and glued to secure it and then trimmed.

After that it’s just a matter of gluing new plastic on the door and vent window frames and mounting all of them back on their hinges.

All Done!

Viola! In about 4 hours the greenhouse is completely re-covered! Now I just have to move the tables and pots back in and it’s ready for plants.

(Hmmm… I just noticed that the birdfeeder in the foreground is broken and about to fall off. I’ll have to fix that.)