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The Man Who Extends The Summer

The Man Who Extends The Summer

A Yukon greenhouse aficionado has given Northern green thumbs a leg-up on winter.
By Herb Mathisen
Jun 28
From the June 2016 Issue

Gardening shouldn’t get in the way of a good canoe trip. So says Bob Sharp, a master tinkerer who has been teaching northerners how to build greenhouses suited to cold climate gardening at Yukon College for the last 20 years.

With that simple premise in mind, Sharp developed a six-piece greenhouse kit that includes both automated watering and venting systems. “I wanted to be able to go away for a week or two and not come back to a dead garden,” he says. The prefab kits can be assembled in as little as 40 minutes and because of an ingenious heat circulation system, they can extend the growing season by two to three months.

Sharp’s been in the Yukon for almost 50 years—having grown veggies in Ross River in the ‘60s, starting up a small garden in Old Crow in the ‘70s and experimenting with different greenhouse designs at the small farm where he and  his wife raised their kids outside Whitehorse for the last 35 years.

“It costs us less than six bucks a year to operate it.” 

The kits, which Sharp manufactures with his son, can accommodate two eight- or 16-foot long beds. Air is circulated through the greenhouse by a recycled computer fan affixed to a PVC pipe. The air is pushed from the top of the greenhouse down through the lower part of the beds, which are filled with rocks two- to four-inches in diameter. “During the daytime, it’s pumping that hot air across the rocks, warming them up and of course, in that process, it’s cooling the air down,” he says. “At night time, when you’re pumping the cooler air across the warmer rocks, it warms the air up and it’s coming out around 14 or 15 C.” This eliminates a grower's enemy: frost. And if it ever gets too hot inside the greenhouse, vents can be pre-set to open to maintain a desired temperature, meaning you won’t bake your plants either.

The whole rig consumes just six watts of power. All you need to do is run an extension cord out to the greenhouse and plug it in. At Whitehorse’s $0.17/kilowatt-hour rate, “it costs us less than six bucks a year to operate it,” says Sharp.

But you wouldn’t run it year-round. “The object here is to really extend the season, not make it into a 12-months of the year thing,” he says. The money you’d spend heating a greenhouse at -30 C would outweigh the savings you’d get through your fresh-grown produce. “The goal is to make the heat gain greater than the heat loss, so you can store the heat and keep the greenhouse warm at minimal cost.”

Since word got out about his backyard kits, Sharp’s been contacted by cucumber and tomato-lovers as far away as Iqaluit and Labrador. He’s honoured, he says with a laugh, and though the kits can fit in the back of a pick-up truck, he’s not going to be shipping them across the country. In fact, he wants greenthumbs to try to build their own. We’re not being proprietary about the design at all,” he says. Sharp has sketches up on his website and he will eventually include detailed animations on how to construct the greenhouse.

But it could be a while before those drawings get posted online because he’s a busy man. In fact, he has to cut our interview short—he’s due at Elijah Smith Elementary School in Whitehorse any minute, where he’ll be putting up yet another Bob Sharp greenhouse.