Extending the Growing Season

We have a 240 day growing season here in the Piedmont of North Carolina, but because I know my climate and am prepared for its whims, I can garden 365 days a year. Of course, I am not picking tomatoes in December, but the garden beds are full of greens, cabbages, root crops and crops that have very long seasons like leeks and garlic, and we are eating out of the garden every day all winter long. We do this through plant selection, ground preparation and on demand shelter.

 In order to grow some of the more tender cool weather crops, or to give newly planted starts a little shelter while they get established, we devised a greenhouse tunnel system that we use on our raised beds as we see the need for them. We have similar systems at the ready during the sweltering days of summer, but since it is cold right now I will talk about our winter bag of tricks for extending the winter growing season. Our garden beds are French Intensive, deep dug, raised beds. The beds are never walked on and they are fed copious quantities of organic matter through mulching and applying compost. The beds are four feet wide and depending on their location, range between 15 to 25 feet in length. The green house tunnels can be set up in a matter of a half hour or so, any time we see the need and will fit any of the beds we have in use.

A simple and inexpensive way to extend the growing season.

The green house tunnels are simple to set up and the material costs are minimal, as long as we are careful to take care of the plastic from year to year. We use a 100 foot long by 10 wide roll of 6 ml. plastic for the tunnel covers. We cut the roll into 5, 20 foot lengths. We seldom need to cover more than 5 beds at a time since many of the things we grow in the winter aren't bothered by freezing weather, so five tunnels is plenty. We start with 1 1/4" PVC plumbing pipe 10 feet long and cut it into 2 foot lengths with a PVC pipe cutter, (which we happen to own since we did our own plumbing, a hack saw will cut the pipe without any trouble, if you don't have a pipe cutter.) Then we drill a hole in the pipe 1 inch from the end through both sides of the pipe slightly larger in diamater than a 16 penny nail., (this hole is useful later when we are wanting to get the pipes out of the ground...more on that later). For the hoops we use 1/2 inch PVC pipe which is sold in 10 foot lengths. We  cut the pipe to 8 foot for short tunnels and use 10 foot pipes for tall tunnels. The 1 1/4 inch pipes are driven onto the ground with the drilled hole end up, using a heavy rubber mallot, (if you don't have a mallot, then use short a piece of 2x4, rest the 4 inch side flat on top of the pipe and hit the 2x4 with a hammer. Don't hit the pipe with a hammer without something to soften the blow it will split the pipe). Drive them into the ground until 3-4 inches of pipe remain above the soil. The pipes should be set opposing each other across the 4 foot wide span of the bed and driven in the ground at 3 foot intervals on each side of the bed.

The 1 1/4" sleeve pipe with the 1/2" hoop set in place.

The 1 1/4" sleeve pipes are in place opposite each other in the bed and  3 feet apart along the length of the bed.

The next step is to determine whether a tunnel needs to be tall or short, tall for things like Fava Beans and peas. short for lettuce, and other greens.Then put the appropriate length pipe in one hole and gently bend the pipe and slide it into the 1 1/4 inch sleeve pipe on the opposite side of the bed. It is easier to do this with two people, one on each side of the bed. If only one person is available, then start in the middle of the length of the bed and work your way towards the ends. This way you are not trying to reach over a hoop that is already set as you work your way from one side of the bed to the other. It is helpful to have a plastic clothes hanger with you so that you can set one side of the pipe, walk around the bed, (never walk on the beds!!), and reach across the bed using the hanger to hook the pipe and pull it to yourself. Bend the pipe gently and slide it into the sleeve pipe. Try to set the pipes at an even height all along the bed by sliding them up or down slightly inside the sleeve pipe until they are a uniform height. At this point it is time to weed the beds, plant your seedlings and water well.

Romaine that was started inside under lights is now in its new home in the garden. They will be given some shelter from the cold while they get established.

 
 When the bed is planted pull the 6 mil. plastic sheeting across the hoops, making sure to have it centered on the hoops so that an equal length of plastic drapes over side to side and end to end. Anchor one side of the plastic to the ground by laying boards, rocks, or other heavy objects along the length of the tunnel, then repeat on the opposite side, being sure to take out any slack to avoid sags that could catch water. Then gather the plastic together on the ends and twist to pull up any slack. pin with a board or other heavy object.

Place the plastic over the hoops and draw up tight to prevent sagging that could catch water or snow and collapse the tunnel.

As long as the days stay around freezing the plants will be safe and warm under the plastic, if the day is above 45degrees, then the plastic should be pulled back on one side to allow air circulation. It can get very warm inside the tunnels if the days are much above freezing, and you don't want to cook your seedlings, so make sure to monitor the daytime temps inside the tunnel. The other end of that is not to forget to cover the tunnels before nightfall if the night time temps are below freezing. As long as the tunnels are in use both day and night to cover the plants you won't have to water very often, since it creates it's own weather inside.Water will condense on the plastic during the day when the sun warms the air inside the tunnel and then when the temps. begin to cool off the water will "rain" back down on the plants. I check periodically every other day or so by sticking a hand under the plastic and poking my finger in the soil to see if it is moist. If it feels dry then I will pull back the plastic enough to get the watering wand in and water end to end. I haven't had to do that very often though. If you are pulling the cover back during the day then you will need to check the soil to see if you need to water before you cover them for the night.


These greenhouse tunnels can extend your growing season so you can grow crops all during the winter. Even in coldest climates the tunnels should give enough protection to grow cabbages, kale, greens, chard, and root crops, where it is too cold for growing things like lettuce, even with some shelter. The tunnels can be used for many seasons as long as care is taken to properly clean and dry the plastic before storing for the summer. The poles will last for years if they are cleaned and stored properly.

An unexpected snow storm covered the winter garden in several inches of snow, which didn't bother our winter hardy crops like cabbage and kale, but without the tunnel, our more tender salad greens may have been ruined. Fortunately, they were snugly tucked in to their greenhouse tunnel, safe and sound.

The tunnel may be covered with snow and the outside temps below freezing, but inside the lettuces are are protected from the inclement weather and the air temp is above freezing.

By using greenhouse tunnels, I have salad greens, herbs, and other cool weather crops fresh out of my garden all winter long. I see substantial savings of my grocery dollars, since I am not buying produce during the most expensive time of the year. The tunnels pay for themselves the first season I use them and then my savings continue to grow with each season they are in use. But the best thing is that  I can pick colorful, nutritious and delicious produce throughout the winter, for very little money or effort.

**When ready to remove the 1 1/4" pipe from the ground slide a 16 penny nail through the drilled holes and pop it up out of the ground by using the nail as a leverage point for a shovel. To extend the life of your PVC pieces and plastic sheeting clean them and store in a dry place out of the sunlight.

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