Launching Some New Ideas: Extending the Growing Season

I very recently discovered just how much I love winter squash. I've witnessed very many a squash get turned into appetizing pot pies and sides. What's more, these squashes come with their own built-in sealing mechanisms, allowing you to store them for months after you harvest them.

The Cold Frame Design Concept
Here you can see what the cold frames will generally look like. The green path you see in between is where I'll run a swale for water harvesting that will also act as my access way to step around my garden beds without stepping on them. Click images for a closer view.

Our rainfall patterns here in Calgary (at 325mm annually) are such that when it rains, it pours... but it just doesn't rain really often (with the exception of this summer past). Our growing season is also really short, with snow ending finally in May, but starting up again in September. We also have really dry air here, because our Rocky Mountains force incoming moisture-filled air from the Pacific really high up, effectively squeezing all of it's moisture down as precipitation into British Columbia. Without this moisture, our air doesn't even stay warm at night, ensuring us with green tomatoes . So these are some pretty tough terms to deal with.

But I assure you, wherever there's a problem, there's always a solution for something else. All it takes is looking at the problem in a different way.

Close-up of inside the cold frame
This is a close up view of inside the passive-solar cold frames. Here you can see how I'll arrange the patio bricks. In April, the angle of the sun will still be pretty low, so I will actually add a second layer of bricks, forcing the back of the cold frame higher, which will angle the south window more appropriately to the lower sun, but introducing more thermal mass, as it will be needed more in the colder months of March and April, when the benefit of thermal mass is more needed. 

Places that don't get a lot of rainfall get a huge amount of sunlight. In fact, in Calgary, we're on par with Florida. We can put this resource to really effective use. Our plant growth pattern in Alberta is very much like our rainfall pattern: when plants grow - THEY GROW! Just as swales and other earthworks can harvest and then store rainwater for use when it's not raining, we can use simple and inexpensive features in our climate to as as a swale for our ubundance of sunlight 

I have recently moved to a new place in Calgary where I have enough land access to manage my own garden (up until now, I've been gardening on other people's land). The first thing I want to do is to figure out how to extend the growing season so that I can grow my beloved squash, and all sorts of other food - in general, transform this abundance of sunlight into an abundance of food so I can store it over the winter. I've decided to take advantage of the principles of passive solar design. My good friend Rob Avis of Verge Permaculture recently completed construction of a passive solar greenhouse in the backyard of his urban property. Essentially, these structures take incoming solar energy in the cold season, which strikes thermal mass inside the building thereby accumulating some of the sun's energy during the day. When the sun goes down, the air temperature eventually drops below the temperature of the thermal mass and so heat then transfers from the thermal mass to the surrounding air in the greenhouse. So exactly how swales "capture" and store water in the soil so it's available for use during dry periods, passive solar structures "capture" freely available solar energy and store it within their bodies so it's available for use when the sun's gone down.

The Cold Frames from the Sun's Point of View
This is what the springtime sun sees. The bricks are clearly visible, so the sun rays will directly strike these thermal mass bricks and begin warming up the soil so my April-planted seeds will have the proper germination conditions.

So what I've decided to try out is a passive solar style coldframe system. My design parameters are: inexpensive, easy to install, and easily replicable so that others can do it. 

The system will consist of twelve identical cold frame panels, each with a window that will face south, and a closed back that faces north. These faces are joined on the top by hinges, making them easy to store during the summertime. Each window will be made be stretching flexible but durable clear plastic over the frame. On the top of each coldframe, there is space between the faces that serves as a vent to let excess warm air escape. The north face of each coldframe will rest on a layer of patio bricks (preferably dark ones) that I should be able to find for giveaway in an alleyway somewhere for free. The purpose of these bricks is to serve as thermal mass for the coldframes to release stored solar energy at night. This layer of patio bricks will be half-buried in soil on the north side to insulate them so that there's a better chance that the stored heat will radiate into the coldframes themselves. To give you scale, the south-facing coldframe panels are 4 feet long X 1 foot wide. Each coldframe will be situated directly adjacent to one another, forming one continuous micro-greenhouse directly over my garden beds. Each connected row of coldframes will also be situated behind each other, providing complete coverage of the garden beds. 

My principle aim with this design is to plant my seeds and seedlings directly into the soil in April, which is relatively unheard of in Alberta because of our cold springs. The coldframes will be installed as soon as the snowpack has melted, as the principle objective is to harness enough solar energy to effectively warm the soil up to an adequate level for direct planting. This is important, because I earlier attended a market gardening workshop where I learned that up to three weeks of growth is lost every time you transplant from started indoor seedlings to the exterior garden. This particularly applies to my beloved squash plants, of whom also require so much time to get started anyway. 

Rear view of the passive solar coldframes
The view of the cold frames from the north. Here you can see the vent that allows excess heat to escape. Notice how the north coldframe face sits on the brick walls. When the project is finished, you will not be able to see the walls from this angle because soil will be mounded there to act as an insulation layer.

I am not worried about our late spring snowfalls, because the snow will slide to the bottom of each coldframe face and then melt, offering springtime irrigation without hurting the new plants.  Now the snowfall has turned into a valuable resource, and I'm already hoping for a lot of them! I suspect I will be able to remove the coldframes in late May or early June. The brick foundation will simply stay in place to continue acting as a thermal mass in the summertime until the plants are tall enough to over grow them completely, and will be waiting to accept next year's coldframe application! I will only be applying this coldframe system to a part of the garden this year, and starting my seeds and transplanting to the rest of the garden. I really want to see the differences in growth and fruiting.

To close, my motivation for this whole initiative is to create a very accessible solution for food production that is based almost entirely from "waste materials". The wood for this project is going to come from visits to Home Depot and other building supply sources, who regularly offer scrap wood for free. The bricks will come from people who have a supply of bricks they can no longer use, perhaps no longer useable to them. The more we can find good use of such waste materials (trust me, there's an abundant supply) and value add them for earth repair projects such as these, the more we can relatively effortlessly create structures that enable food, water, and energy security for ourselves and our communities. I think these coldframes will end up looking quite beautiful as well, and one will never know they were built out of such waste streams!

I will be writing about every step along the way for your curiosity and information. Thanks for reading!

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Extending the Growing Season!

The passive solar cold frames look brilliant - what a great way to inexpensively get veggies started earlier. I bet a lot of the cool weather crops, including spinach, which is always one of the first things I get to harvest each year, could be started weeks earlier with these. Post pictures!

PS. There are lots of early-maturing winter squash that do well in our climate without any help! I've harvested spaghetti squash, butternut (Hyb. Early Butternut) and pumpkin (Racer) - they're all between 75 and 90 days, and I've had good success both starting them indoors and transplanting out and direct sowing (especially the pumpkin).

Thanks for the info

Thank you for this! I'm going to try and get those varieties!