Defying winter with a greenhouse
There is one annual migration not expected this winter: that of the snowbirds.
Sure, there will be Canadians who head south for the cold months. But of those we know personally, most have decided to stay close to home this winter.
And with the thought of stranded snowbirds looking forlornly at the coming snow — and longing for the greener, warmer climates that have become part of their lives — we think of greenhouses.
Much of our greenhouse inspiration comes from another far-off and out-of-reach destination: the United Kingdom.
From the humble allotment glasshouse, to the orangeries of Kew Gardens and Kensington Palace, the British have a long history of employing architecture for the joys of year-round gardening and sunny solace.
If you find yourself imagining this sunny escape in your own yard, here are a few things to consider:
Municipal zone limitations. The easiest way around this is to think small: A stand-alone structure under 108 square feet will exempt you from requiring a building permit under the Ontario Building Code. Anything larger, or as an addition to an existing structure, will require you to apply for and obtain a permit.
Function. Will this structure serve as a sitting room, or do you plan on maximizing your winter kale production? While we are happy sipping our tea under a large poly grow tunnel, we can appreciate that you might have pictured something more elegant.
Consider whether your greenhouse is simply for seasonal extension, like a large cold frame, or if you plan to heat it through the winter. Which leads us to …
Cost. The range is huge — starting with DIY builds under $500, the sky’s the limit as far as what you can spend. Here are some guidelines:
> At the luxury end of the range, expect to spend around $350-$500 per sq. ft. for a serviced, aluminum-frame greenhouse with some architectural flair. Mark’s sister Nora recently built such a unit using a prefab aluminum greenhouse structure atop a brick foundation. And it looks pretty slick.
Throughout the winter, it houses her tropical plants such
as bougainvillea and Kimberly ferns that create an oasis around her small lap pool in summer. As an alternative to a Florida home or cottage, it is quite economical, not to mention the cost and burdens of travelling.
> Mark’s greenhouse is slightly more practical: A cedar-frame kit with cantilevered windows for ventilation. In the spring, a small electric heater keeps tender seedlings frost-free.
> For the even more practically minded, there is plenty of creative opportunity to reuse materials to create a basic structure covered with poly film; this will run you about 15 cents per sq. ft. Commercial nursery farms often use poly
greenhouses, referred to as “poly tunnels.” The two ends of the greenhouse cost the same, whether it is 30 feet long or 100 — so stretch it as far as you can! Ventilation. Insects and fungal diseases thrive in the warm, humid environments of a greenhouse. Higher-end builds and kits include ventilating windows built into the design. DIYers ought to keep this in mind. Locate your greenhouse crosswind in a breezy area to minimize the number of fans needed to keep the air circulating.
Heat. At the historic Lost Gardens of Heligan, in Cornwall, England, the 200-yearold, refurbished Pineapple House is heated with rotting
compost that helps provide pineapples year-round. Another low-tech, sustainable solution is to place a large thermal mass, such as a barrel of water on the floor of a heated greenhouse to absorb solar heat during the day and radiate the heat at night.
If you are planning on heating right through the depths of winter, however, a gas furnace
is likely your best bet as electric heating can get expensive quickly.
A greenhouse can be a great place to relax or indulge your gardening passion. And, this year, it can be a sanctuary for snowbirds.