High tunnels might just be the answer to every Alaskanʼs dream garden.
A simpler version of a greenhouse, high tunnels have been successful in protecting crops from cold and rainy weather. They also alleviate the constraints of a short growing season, as is the epitome of farming in Alaska. They allow growers to plant earlier in the spring, and help keep crops in the ground even after the ﬁrst frosts.
“You take some of the risk out of our conditions,” said Meriam Karlsson, professor of horticulture at University of Alaska Fairbanks. It stays about 10 degrees warmer inside the high tunnels during any given season, so plants can keep growing even at 20 degrees. “Some years we donʼt get much beneﬁt in the spring, because like last year, it got warm so quickly you could plant outside. The most beneﬁt is usually in the fall,” she said.
While high tunnels do not need electricity for fans, artiﬁcial light, or heat like some greenhouses, they may require more maintenance since it is necessary to open the sides during warm days for a ﬂow of fresh air.
Growing inside of a high tunnel is also different from a greenhouse where crops are grown in pots. “You usually grow in the ground, in the ﬁeld that was there before it, in the soil that was there when you put it up,” Karlsson said.
During the winter, most high tunnel users remove the plastic cover so snow and wind are not a problem. There are exceptions, particularly in the case of two apple tree tunnels at UAF. The plastic was left up to protect the perennials from a deep freeze, but the snow load proved too much weight for the structures.
The 42-foot-wide, 96-foot-long, 26-foot-tall giants, used to house over 100 apple trees, both caved in after rough Interior winters.
“Everyone says, why didnʼt you take the cover off, why didnʼt you take the snow off? Well, we couldnʼt really because itʼs hard to get up there, especially during the winter, and you get into all kinds of liability issues with the university,” Karlsson said.
Being as large as they were, even after the necessary precautions were taken with Risk Management, it was difﬁcult to remove all the snow and ice buildup from the center of the elephantine structure, even with a cherry picker.
The apple tunnel project was initiated by Dr. Bob Wheeler, a forester working for Cooperative Extension Service at UAF. When he began the research he did not have any experience with high tunnels. “I think he was just getting really excited about the possibility of being able to grow fruit and things that people don’t usually grow here with the use of these structures,” said Kendra Calhoun, who was hired as a research technician for the high tunnel apple project in 2007. “It was more of an apple project than it was a high tunnel project.”
Before he passed away in 2009, Wheeler took the initiative of taking care of the tunnels.
“He was really out there all the time himself working and trying to get the snow off,” Karlsson said.
After his death, the tunnels were left in limbo, as the Cooperative Extension still owned them, but they were situated on UAF’s Experimental Farm, so there were differing opinions on who was responsible for them. “Everybody thinks that we should just take care of them,” Karlsson said. The funding ran out shortly after Wheeler’s death, and the project was passed on to Karlsson.
The remainder of the tunnels have been removed from the Farm.
“It’s possible we could have salvaged and made a smaller high tunnel from what was left over from those tunnels collapsing, but there’s just no money to put the time and there’s nobody who wants to do it, so they just let them go,” Calhoun said.
The plan is to uproot the trees and use them for landscaping purposes throughout campus. “We can’t just leave it and let it go to weeds or whatever, it just doesn’t work,” Karlsson said.
“I just think they’re too big to manage. I don’t think it’s anyone’s fault necessarily, they’re just too large for this climate I think,” Calhoun said.
UAF has four other tunnels a fraction of the size of the apple tunnels at 12 feet by 24 feet, and one double-tunnel that has two sections, each 26 feet by 48 feet. After the crops are harvested, the greenhouse grade plastic is dropped in the middle of the structure and stored there for the winter. These tunnels have been successful with annual crops, and depending on how the plastic is stored, it lasts for about four years before needing to be replaced.
High tunnels are becoming more popular in Alaska, particularly on the Kenai Peninsula. Shipping to Alaska doubles the cost of a high tunnel, but using local resources could make growing in one more feasible.
“I think it’s really well worth doing,” Karlsson said. “There is a lot of opportunity, and you do get benefits from tunnels up here.”