Welcome to a series of blogs about Cultivate Cochrane president Jackie Skrypnek’s backyard greenhouse building process. The intent is to share a realistic account of one couple’s experience to help inspire and inform other community members in their own season-extending, food-producing ventures.
With our little home for plants more or less complete, the only thing left for us to do was furnish it and help them move in!
Building beds on the south side turned out to be just a little more involved than I had imagined. We needed to raise the soil height far enough up so the knee wall wasn’t shading the plants from the incoming light. But we couldn’t have that bed in turn shading plants growing just a short distance away against the north wall - those ones would be near ground level to allow vertical space for a shelf as well. We settled on a two-tiered south bed so the height (and shadow cast) would make one step down. I would probably have simply heaped soil against the greenhouse wall and held it back with lumber. But, knowing a thing or two more than me about construction, my husband wisely built four-sided boxes in place to contain the weight of all that soil and water and prevent the knee wall from bowing out over time. Cedar would have been a lovely choice, but it’s pricey and we had some spruce boards already on hand. So we used Lifetime once again to treat them (it’s non-toxic for gardens) and crossed our fingers that they won’t need replacement for several years!
Inside the boxes, we took the sod we had removed earlier, laid it upside down with a layer of cardboard overtop to suppress it from growing back up, and proceeded to fill the deep space with soil. For the bottom foot or so, we used soil we had set aside from our perimeter excavation - quite a bit of rock and clay, but that would be fine as a subsoil layer. We topped that with a mix of better soil also set aside (from just below our excavated lawn), NutriLoam from Top Spray, and well-composted manure from a ranching family member.
The north bed is much more shallow so, after removing the sod layer, we laid down cardboard to help prevent grass popping back up and topped it with the NutriLoam and manure. I had to cut holes in the cardboard to insert tomato plants this year, but by next year that barrier should have broken down. These beds are fully connected to the earth below and all the soil microbiology and nutrients that come with that, whereas the shelf of pots we placed higher up will need their structure and fertility completely renewed each year. We’ll see how the two scenarios compare.
More sidewalk blocks on the floor add to the thermal mass, but we could still use more (the amount needed can be roughly calculated based on square footage of glazing and the heat capacity of your thermal mass material). To this end, I wanted to contain the north bed with upright flat stones we’d inherited from a neighbour, but we quickly realized this was a recipe for endless pockets of weeds (not to mention tripping over sharp, protruding rocks!). Instead, we used the very last of some stashed cedar we had and simply stacked some stones between plants in the bed to achieve a little extra thermal mass.
We plan to play around with adding a flip-down seat or two, maybe a little shelf at table height to set a book and a drink. One corner will host a grapevine which we hope will have no trouble over-wintering. And we’ll direct rain off the south face into a barrel or two for easy watering (while it lasts). But mostly, we’re ready to sit back, enjoy this space and see how it performs. Populated with plants and seeds, it’s finally serving its purpose, though I worry that after all this work and expense I’ll discover I’ve grossly miscalculated something and the greenhouse inhabitants will fail to thrive. But with nearly two weeks under their belts, the plants seem to be quite happy with their new home.
My husband and I even spent our anniversary in there sipping cider and sharing pizza from one of our best local establishments. If all goes as planned, we’ll still be enjoying this warm enclave when the snow flies in earnest, usually sometime around Halloween. If we’re basking in our greenhouse at Christmas, that would be a wild success and we’ll be sure to let you know!
