My Adventures with Trial and Error Greenhouse Gardening

November 17, 2019

One should never assume anything, especially when it comes to weather. Past weather patterns, at best, provide some predictability. More importantly than this, is to be prepared to readily adapt.

Climate change is bringing us more blasts of extreme cold as the polar vortex extends further south. This past week has seen the temperatures drop on our farm to minus 18⁰C, a reminder that weather patterns are changing and to never take anything for granted.

I had a fair number of vegetables in the garden which I expected to harvest into December with some protection (carrots, beets, rutabagas, cabbage, herbs, etc). But, when meteorologists predicted the imminent arrival of an Arctic air mass, I pulled up whatever was left in the garden, knowing that I may not be able to successfully harvest as anticipated. Some went into our root cellar and some into the greenhouses to continue growing.

In this climate, it really helps to create a microclimate to control growing conditions. It is also important to keep heating costs to a minimum so that the cost of energy doesn’t outweigh the benefits of a fresh harvest. The less energy we use, the less impact on the environment.

As I mentioned in an earlier post, I got into greenhouse gardening when we set up a greenhouse for the native plant nursery in October 2008. I felt the warmth on a sunny day and wondered why I wasn’t using the space to grow our own greens. So, I brought in some good soil and started seeding directly into beds that I built out of cull lumber.

It was very gratifying to see radishes, lettuce, chard, spinach and kale germinating in October, just when our gardens were coming to an end.

Even though these are all cold season vegetables, I thought I needed to heat the greenhouse to keep them alive. I tried a propane heater and then kerosene. Both failed miserably and the latter caused a lot of grief by spewing soot all over the plants and plastic greenhouse cover.

I got the message. If I couldn’t make this work without additional heat, it was best to abandon the idea.

A challenge is the mother of innovation. I needed an inexpensive heat sink for absorbing solar heat during the day and for slow release of heat during the cold nights. We filled a large number of 2 litre plastic bottles with water and hung them on the greenhouse frame. The water would warm up during the day, release heat during the night and freeze, then thaw and warm up on the next sunny day. But, success of this method was very limited. Heat rises. Most of the warmth went out through the plastic. In spite of this, we were able to harvest a fair amount of produce for ourselves into late fall until the ground froze. With no liquid water available, the plants died back.

Then, to create a more confined microclimate, I placed 6 foot wire hoops over the beds every metre or so and covered the beds with frost blankets each evening and removed the blankets each morning after the temperature rose above freezing. This sounds like a lot of work, but, once I had a system in place, I was able to cover and uncover the 150 ft of beds in about 5 minutes. I placed stepping stones every

couple of feet down the centre of the beds to act as heat sinks. Under the blankets, it rarely dropped lower than about – 8⁰ C, even on brutally cold nights. However, the ground still froze during the coldest months of the year.

     Then, I thought of heating the stepping stones. I found a relatively inexpensive 115 watt 25’ underground cable that is thermostatically controlled. I then placed it under a row of small patio stones or field stones down the centre of one of the 5 ft beds. The stones are gently heated and frost blankets covering the beds create a great microclimate that keeps much of the soil from freezing. When you flip off the frost blankets in the morning, there may be frost on the foliage but the roots are not in hard, frozen soil. This method has allowed us to harvest greens throughout the winter, at least enough for family.

The best insulated clothing is light with lots of air spaces, just like leaf litter traps air and has great insulating potential. With this in mind, a cold frame greenhouse is best covered with 2 layers of plastic or glass to create an insulating dead air space. A 12 volt fan can be used to pump air between the 2 layers of plastic to keep it inflated. The inflation also helps the greenhouse shed snow. The snow that slides off the greenhouse is full of air spaces and so is effective insulation at the ground level.

The coldest days are typically the sunniest. It is not unusual to enjoy a balmy 20⁰C inside the greenhouse when it’s well below freezing outside. Creating a microclimate like this, is a real boost in winter between doing that little bit of gardening and having fresh produce to put on the table.

It’s not expensive to maintain a greenhouse like this once you have the cold frame structure, heating cable, wire hoops and frost blankets. We have hydrants in the greenhouse and hoses for watering. But, you rarely need to water during the winter because, inside the greenhouse, you have evaporation from the ground, condensation on the plastic, and precipitation back onto the ground. It’s like being in a closed terrarium.

If you already have a greenhouse in your yard, it wouldn’t take much for you to grow your own lettuce, endive, chicory, spinach, kale, oriental greens, collards, chard, beets, corn salad, winter purslane, arugula, green onions, green garlic, celery, parsley, thyme, sage, rosemary, oregano, mint, dill, and cilantro. All of these vegetables and herbs can handle a lot of cold.

What’s not to like about a bountiful harvest of fresh greens and herbs in the winter.

Nature will challenge us at every turn. This year brought us a prolonged cold, wet spring followed by a drought, a gentle easing into fall and then a sudden drop in temperatures well before the Winter Solstice.

We just need to remember that the Earth is a relatively small sphere of rock, water and gases moving at a speed of over 100,000 km/hr while spinning in dark and hostile space, orbiting a star that provides the energy for life to thrive but can also destroy life. It is truly amazing that our planet hosts so much beauty, dynamic weather patterns, landforms and phenomenal diversity of life.

It doesn’t take much to disturb the fragile atmosphere and surface on which we live.

There is no occupation more humbling and fulfilling than that which brings us into sync with natural flows, cycles and disruptions. We feel the pulse of the Earth and work with the changes that happen while recognizing the powerful human influence on the delicate stability of this amazing home of ours.

Published by Natural Themes Farms

A small scale farm located in Frankford, Ontario specializing in working with nature to grow and sell: * North American trees, shrubs, wildflowers, vines and ferns. * fruits and vegetables, grown without the use of chemical fertilizers or pesticides.

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