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Gardening and More: Grow tunnel can extend your gardening season through the winter

HOW DOES YOUR TUNNEL GROW? — This photo shows the grow tunnel when it’s open. When closed, the plastic tarp is folded over the opening. You can use a grow tunnel to extend the season, for certain vegetable crops, into fall and winter. Photo by Connie Oswald Stofko.
BUFFALO — Winter weather is definitely here. We’ve had temperatures in the teens and we’ve had snow. Most of us have packed up our gardening equipment, for the season.

But, at a school garden here in Western New York, they’re still growing vegetables outside.

A simple structure called a grow tunnel has allowed them to extend the growing season, according to Caesandra Seawell, garden manager for the City Honors School garden, also known as Pelion Community Garden, in Buffalo.

They are growing “third-season crops” that can tolerate cooler temperatures: broccoli, kale, chard and kohlrabi. Other cool-weather crops that you could try include carrots, cabbage, turnips, parsnips, beets and collard greens. You can even grow Brussels sprouts in a grow tunnel, but you have to be patient – they take about 90 days to reach maturity.

The plants were all seedlings in the fall or were plants that had been growing in other beds. Even if the plants freeze and don’t make through the entire winter, they will be the first to come back in the spring.

Seawell hasn’t had as much success with seeds. She tried sowing some spinach and beet seeds in early November, but those haven’t sprouted and probably have died, she said.

A grow tunnel or small hoop house is inexpensive to build. Seawell estimated the grow tunnel probably costs less than $50.

Seawell and her students started with a raised bed 18 inches deep.

To form the frame, they used six pieces of rebar, each 4 feet long. Using a stake pounder, they drove four of the pieces of rebar into the corners of the bed, then drove the last two pieces along the sides, halfway between the corner pieces.

To form the arcs, they used1/2-inch PVC pipe. That type of pipe is flexible, according to Seawell; larger PVC pipe is not bendable. They slipped the PVC pipe over the rebar, to form the arcs. Seawell said that if your rebar is cut at a slant, it makes it difficult to slip the PVC pipe over it, so make sure your rebar is cut straight across.

The covering is a 6-millimeter plastic tarp. Keeping the covering in place has been a challenge, because the bed is located in a windy spot. Seawell used plastic clips from the plumbing section to attach the tarp to the PVC pipe, but high winds blew the tarp off. So, on two sides of the bed, she nailed the tarp to the wall of the bed, sandwiching the tarp between the wall and pieces of 1-by-4-inch wood. She kept the front and one side loose, so she can access the interior to harvest the plants and water them, if she needs to.

Bricks help hold down the tarp on the side that’s not nailed down, but when it got windy, the clips blew off again and the tarp opened up.

Seawell is looking for a better alternative to the plastic clips, and said she’s also considering orienting the grow tunnel differently, so the wind won’t be as much of a problem, or placing the grow tunnel in a spot that’s not so windy.

She also placed whole bags of leaves on the windy side of the tunnel, to act as a wind breaker. The leaves are in clear plastic bags (she found the leaves bagged up at the curb), but noted that if they were in black plastic bags, they would absorb and hold in more heat, which might help keep the interior of the grow tunnel warmer.

Seawell is also going to be watching to see how the tunnel performs with snow. If there is a lot of heavy snow, she may use T-connectors to put a spine across the top and make it into more of a V-shape and less of a U-shape, so the snow slips off better. Because it’s not that large of a structure, it may not be a problem.

A grow tunnel is a simple structure that you can make to help extend the gardening season.

Connie Oswald Stofko is publisher of Buffalo-NiagaraGardening.com, the online gardening magazine for Western New York. Email Connie@BuffaloNiagaraGardening.com.


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