And Then There Were Two (Greenhouses)

Reader Contribution by Cam Mather

Part of my goal in running a CSA that will supply a dozen families with produce over the summer is to extend my growing season. In terms of extending the season at the beginning I got off to a slow start, because I didn’t get my greenhouse built in time. But I plan on coming on strong this fall after I got my first (glass patio door) greenhouse built.

Then I started thinking about the raised beds in the barn foundation. They have always been a great place for heat loving vegetables (peppers, eggplants and tomatoes). In the past I’ve had two problems with these gardens.

My first problem was moisture. Since they are raised beds, sitting on the concrete floor of the old barn, they tended to dry out fairly quickly Also, the soil always ended up with a hill in the middle and water tended to run to the sides whenever I watered.

The second problem was our pesky early frosts here. We’ll often get a frost in September that will kill a lot of stuff. Then we may go another month before our next frost hits. This drives me nuts. I just knew that if I could protect the plants from the first frost, they’d keep producing for the rest of the frost-free month, but I had no convenient way to protect them.

So last fall when I borrowed Heidi and Gary’s backhoe, I started moving soil from outside of the barn foundation into the raised bed area. As always it was a crap load of work, because the bucket wouldn’t fit through the door. So I had to shovel it by hand into the area between the two raised beds. I decided if I was going to cover this area I might as well optimize how much garden space I was protecting. This also meant that I’d have more soil in the one garden and a more level surface to allow water to be absorbed and not run off so much.

So after I finished the glass greenhouse (shown here)  I started work on this second “greenhouse.” Really, it’s just a raised bed that I can conveniently cover during cold nights. As always cost is my biggest parameter. I bought some cedar posts locally, which were about $4 each, then some spruce 2x4s for the cross pieces on top. An 8 foot spruce 2×4 is $2.50. How is it possible to cut that tree, strip the branches and bark off, ship it to a mill, cut it down to size, and then ship it to Home Hardware in Napanee, and still be able to sell it for $2.50? The mind boggles.

Then I got really lucky when speaking to my friend Ian Graham who has greenhouses. One of Ian’s greenhouses had been damaged and he ended up with a section of plastic that he offered to me (when I asked, of course). When our friends Ellen and Jerry came for a visit to deliver our new blueberry bushes they were able to bring the plastic too. Thanks Ian! It’s awesome! And thanks Ellen & Jerry too!

So here it is, my second greenhouse. Yes, it’s fairly low, but I did this intentionally. I didn’t want to pay for a commercial steel greenhouse and I didn’t want to engineer one that was tall and have to deal with wind forces. This one is low and surrounded by the barn foundation wall. Yes there will be wind but I think with the low profile and natural wind break of the walls it shouldn’t be too big a problem.

Once the danger of cool nights is past I may take the plastic off for the rest of the summer and potentially some of the 10-foot stringers. I’m not saying that it’s likely I’ll forget they’re there and whack my head, but it is a possibility. And if it was to have happened already, I’m happy to report there was no concussion… that I know of… well at least not that I noticed after I came to.

Filling in the space the between the two separate raised beds was a stroke of genius. I can’t believe how much better this garden is holding moisture. There’s just more soil in it, and with a uniform flat top it’s doing a great job of being one less thing for me to worry about. There were times last year when I’d get over-worked in the main garden and forget to water these beds which would put the plants under real water stress.

Right now I roll the plastic up in the morning and roll it back down after the sun goes down. I love stepping inside under the plastic in the morning before I roll it up. It is noticeably warmer than outside. And the air is really moist. There is a lot of condensation, which drips off the plastic and falls back down on the soil. I’m not sure if I’d be losing that moisture at night if I didn’t have the plastic over it, but regardless, it’s nice to see the water staying where it’s needed.

And yes, I should shut up and spend money and buy a real greenhouse!

I’m getting there. What these two projects are allowing me to do is evaluate just what I can achieve with an unheated greenhouse in our northern climate. If I can increase yields and extend the season enough, then yes, I’ll bite the bullet on the big one.

With projects like this sometimes I like to move slowly and understand exactly what it is I’m trying to achieve. It seems very common to me for people who want to start growing food (and have the money) to just put up a greenhouse. I’m just not sure they take full advantage of it. I’m hoping that once I understand its benefits I’ll be better able to decide how much to invest in a larger greenhouse.

For now I bought some cedar posts, some 2x4s, some screws and got the plastic for free. I’m well under $100 for this greenhouse.

Oh yes, and if I were smart I’d factor in the expense of a proper hard hat that I’d force myself to wear whenever working in the greenhouse as it’s configured now, otherwise I may not have the brain cells left to figure out how to build a greenhouse of standup height!

For more information about Cam or his books, please visit