Construction of the Greenhouse

(By John)

In the last post, we discussed the technical aspects of how unheated greenhouses are supposed to work.  In this post, we discuss the actual construction of the greenhouse.

        

    Once we had done our research, we then turned to the question of actually turning our small (6’´6’) front porch into a greenhouse.  The main criteria were that:

1.      The construction would need to be easy, and

2.      The materials needed to be really, really cheap.

Keeping this is mind, we began our search.  The plastic sheeting had to be tough, yet still let a large amount of light in.  Most of the rolls of plastic were too opaque.  In the end, we ended up buying three rolls of much clearer four mil insulating plastic intended for covering windows during the winter.  We got the outdoor variety, as the indoor kind seemed too flimsy.  We also got a few rolls of clear indoor/outdoor tape and outdoor duct tape.

All in all, everything came in at under $40.  We scrounged a few plastic drain gutters from the basement, and got to work. The total labor (carried out by Dad, my brother Paul, and me) lasted about three hours.

The greenhouse from the side.

The greenhouse from the other side.

At first, we were a little put off by a potent chemical smell inside the greenhouse.  Was this bad for us?  Was it bad for the plants? Would it be bad to ingest plants that had been exposed to it? Was there not enough air circulation?  Luckily, the smell dissipated in a few days, largely due to our high-tech venting system. (Okay, the vent was originally due to a mistake while taping, but we made the most of it once we found out.  It's shown below, posing with a giant foam puzzle piece to hold it open.  It may look a little odd, but it works.)  

The air vent.

It had occurred to us, of course, that some sort of venting was needed.  We thought that the air coming through the slats in the deck, from the house, and from any little spaces in the plastic (this is far from an air-tight enclosure), would probably be enough.  We usually keep the vent closed, opening it on the rare occasions when things get too hot. 

The greenhouse from the front

Little Greenhouse in the Snow

(By John)

We got two inches of snow this morning.  The plants seem fine.

Pea plants

Lettuce, chard, and spinach

Marigolds and petunias

The Idea Behind Unheated Greenhouses

In the last few posts, we have related how we became interested in and started looking into unheated greenhouses.  In the process we encountered The Winter Harvest Handbook, a book describing how a Maine grower has been successfully using unheated greenhouses for years.  We gleaned some very useful information from this book…

(By John)

            Reading through Eliot Coleman’s book, I was fascinated.  I also learned some of the limitations of unheated greenhouses.  Overall, however, it appeared that an adaptation of his basic method would be highly doable.

             One important point to stress from the start is that we’re not talking about growing tomatoes or watermelons here.  A major reason that going unheated was so appealing was that no snazzy or expensive equipment was needed.  Obviously, using plants that don’t mind the cold as much means that you can still get a decent harvest without maintaining a July-like temperature inside.  This leaves mainly hardy, leafy vegetables like lettuce, spinach, kale, chard, kohlrabi, and the like, as well as root crops such as beets and carrots.

            A second point was that maintaining a slightly warmer temperature was not the only way the greenhouse would protect the plants.  Although cold temperatures are clearly part of the reason that plants can’t normally survive the winter, wind and humidity are also huge factors.  Without the effect of the dryness and the wind, our vegetables would do much better even without the benefits of a warmer climate. 

As of today (Nov. 13th) these marigolds have spent 10 days in the greenhouse

            Back on the problem of temperature, it seems hard to believe that plastic wrap would do that much to keep off the cold.  This is why having two layers is so important (right now we’re covering the young plants with sheets at night; later, we may need another layer of plastic) .  In an unheated greenhouse, the combined effects of no wind, increased humidity, and slightly elevated temperatures make it like the plants have been moved 500 miles south.  Adding a second layer to protect against the bitter cold of the winter nights moves them another 500 miles south.

These marigolds, from the same bed as above, stayed outdoors (Nov 13th)

            Ideally, we would have started the planting in August.  Still, although October is definitely not the ideal time for planting, we should still get something.  The project could work; now all we had to do was actually get it going…

In the next post, follow us through the construction of the greenhouse.

Will An Unheated Winter Greenhouse Work In Maine?

In the previous post [here] we told of how a friend's off-hand comment inspired us to turn our tiny front porch into an unheated greenhouse - but we still didn't know if it would even work here in the Maine winter.

(by Linda)

Time for some research:

Eliot Coleman's The Winter Harvest Handbook

Naturally, the next step was to ignore whatever pressing but obnoxious task  awaited my attention (balancing the checkbook and paying bills, maybe?) and do some googling.  Was it even possible to grow anything in an unheated greenhouse in Maine in the winter?  (of course it had to be unheated since the whole point was to save some money on food- though having fresh homegrown veggies was a big plus too, not to mention the coolness factor of the whole thing).

        I first got sidetracked by looking up things like how many hours of sunlight various vegetables needed each day, but quickly gave that up as it was way too discouraging, and I was far too enthused to let a bunch of nay-sayers rain on my parade.

Then I ran across Eliot Coleman (find his website here), a gardener actually living in Maine who had been successfully growing veggies in unheated greenhouses for years- and had been thoughtful enough to write a book about it that was actually in the library system.   A little click of the mouse to request one more inter-library loan, and away we go…

An Idea Is Born: A Do-It-Yourself Winter Greenhouse Down East

(By Linda)

It begins:

Really, it was all Margaret's idea, though I don’t know if she realized I'd take her seriously at the time.  We were talking on the phone a few weeks ago, catching up, and in response to my casual comment that it was really hard to feed 4 teenage boys (ok, I exaggerate; one won’t be a teen for another 5 months), not to mention the other 3 people in the house, she suggested that what we needed was a greenhouse so we could extend our growing season.  The idea settled into my brain like a little seed, took root, and soon began to send forth a perky little shoot.  Sure it's Oct., not exactly the beginning of the gardening season in Maine, but who wants to wait until the spring to try out an idea this good?  Why not start a greenhouse now and just plant cold-loving vegetables?  

Our back yard in winter: how can we keep gardening year round here in Maine?

The plan takes shape: 

Building a real  greenhouse would obviously be way too expensive and time-consuming, so we needed a way to efficiently design a thrifty alternative with user-friendly construction techniques (in other words, I wanted to slap together something really cheap that would take almost no time to make.)

     The obvious path was to cheat and just close in our little front entry deck with some sort of cheap-o plastic sheeting.  It already had a floor, roof, and wooden posts to attach the plastic to, plus being right up against the house, it would probably be warmer than something that was free-standing.  PLUS it got some nice morning sun, as it faced southeast, and we had already grown lettuce there quite successfully for several summers in these nifty planters that have grooves on the bottom so they can sit right on the deck railing (donated by Jenna when she was ditching stuff for The Big Move- thanks, Jenna J )  PLUS we would be able to harvest stuff by simply opening the front door – no trudging through the cold and snow to get to the crop (notice that I am assuming there will be a crop and cold and snow at the same time.) 

     I should point out that in Maine, at least for some of us, the front door just isn't used as the entrance to the house.  I know that's a big Feng Shui no-no, but that's just the way it is.   I figured in the unlikely event that we had to exit really quickly in case of a fire or some other dire emergency, it would be pretty easy to rip through some glorified plastic wrap. 

Next time: an intriguing idea . . . but can it work?