If you’re looking for a way to extend your growing season without breaking the bank, low tunnels could be the answer. These structures are a great way to get started in season extension without making a big investment, and they’re also portable, so you can move them around or take them down at the end of the season.
West Virginia produce growers should make extending the traditional growing and marketing season a high priority. One way to do this relatively cheaply is to use low tunnels. Low tunnels are temporary structures that are around 4 feet tall and 3 to 6 feet wide. They consists of hoops made of wire or pipe, over which is stretched spun-bond fabric or polyethylene plastic, creating a mini greenhouse effect over the crops.
Low tunnels are a type of temporary structure that is easy and inexpensive to construct. They can be used to help extend the growing season and overwinter crops. Low tunnels can also be used to protect crops from cold weather and wind, as well as from insects and high temperatures in the summer by using shade cloths.
Why Low Tunnels?
A low tunnel can be used to protect your plants from the cold.
Crops that are started indoors in January or February and are transplanted under the protection of a low tunnel can be harvested an entire month earlier than if they were not protected. This protection allows for earlier harvests in zone 7 gardens in Arkansas.
Crops that are started indoors during the hot and humid days of July and August can be transplanted outside in September. Low tunnels keep these delicate crops from freezing well into December, with some years going as far as February.
A salad made with fresh ingredients from a garden is a great addition to a Valentine’s Day dinner. It’s a good way to use up produce that would otherwise go to waste, no matter what time of year it is.
Tunnels can also be used to extend the summer garden.
Each year, large stores offer tomato, pepper, and other heat-loving transplants to gardeners who are tired of winter. And every year, people who are eager to get started buy all of the transplants for the season, only to lose them within a week or two. (Unexpected cold snaps or cold, drenching rains are inevitable parts of spring.)
Again, low tunnels provide protection. They protect crops from short periods of cold and the soil from chilling rains, especially when used in raised beds.
Warmer internal temperatures and elevated soil levels make it possible to grow summer crops without the use of expensive greenhouses.
The purpose of low tunnels is not to create summer-like conditions, but to protect heat-loving plants from the last days of unpredictable spring weather. Low tunnels do this by collecting solar heat, blocking chilling winds, and avoiding soaking rains.
The temperatures inside a low tunnel generally stay 10-30 degrees Fahrenheit warmer than the outside temperature, depending on the materials used.
Transplants that need a minimum of 60 degrees will not do well in the low 20s for an extended period of time. In this case, you will need a different method of cold protection.
If you have crops that can withstand cooler temperatures for extended periods of time, you can prevent them from becoming frozen by adding an extra layer of insulation.
A low tunnel can be created by draping sheets of translucent plastic sheeting over the tops of semicircular frames.
Most frames have their ends inserted into the ground between 3 and 12 inches, depending on how stable the overall low tunnel needs to be. This is highly dependent on wind intensity and the frequency of heavy rains.
However, you can build frames with a base that allows you to lift entire sections of the low tunnel off of plantings during harvesting, just like a lid.
The shorter the height requirement is, the better it is. This allows heat to stay close to the ground, which helps plants stay healthy during periods of extremely cold weather.
You should buy materials for your frame based on the maximum height of your crops, plus a few extra inches. This way, the leaves won’t touch the covering, which could cause them to get frostbite during cold weather.
Where to Buy
The materials you’ll need for this project should be easy to find at your local hardware store. You’ll need some translucent plastic sheeting to use as a cover, and then either PVC pipe, rebar, conduit, or 9-gauge wire to build the frame that will support everything.
Most hardware stores will have rolls of plastic sheeting available, with lengths ranging from 10-100 feet, and widths from 8-20 feet. The thickness of the sheeting will vary, from 2-3 mils up to around 10-15 mils. However, it is also possible to find sheeting that is up to 100 mils thick online or at specialty supply stores.
When deciding on a thickness for your plastic, it is important to consider how much light will be able to pass through it. The thicker the plastic, the less light that will be able to enter the low tunnels. Additionally, make sure to add an extra 5 feet of plastic for each end of the tunnel. This will allow for the plastic to be tightened and tucked in order to keep out wind and rain, as well as to retain heat.
Choosing what materials to use for your frame is mostly a matter of personal preference. You can use whatever you like as long as it’s within your budget.
Consider rebar and conduit when planning for stability during high winds and heavy snow loads. Both can be curved into a half-circle shape to allow for the draping of the sheeting.
PVC pipe is a popular choice for many reasons. It is relatively inexpensive and easy to bend (when it is warm outside). It is also very durable. However, PVC pipes can leak chemicals into the surrounding soil unless they are made of food-grade materials. Additionally, PVC pipes can be difficult to bend in cold weather and are more likely to be damaged during high winds or heavy rain.
Nine-gauge wire is a great option for someone looking for an affordable, easily-maneuvered and compact wire.
The wire is not a good material to use in environments with high winds or heavy rains because it bends down towards the soil, often crushing plants.
Materials & Construction
Before placing a low tunnel over crops or raised beds, the ground should be prepared by tilling it.
Most low tunnels are 3 to 4 ft. wide, but you can also find ones 6 ft. wide for vining crops. You can construct your own low tunnel in an afternoon with supplies from your local hardware store or from a kit.
Materials that can be used in the construction of hoops are:
PVC or Conduit
You will need either half-inch or three-quarter-inch PVC pipes that are eight feet long, as well as half-inch steel rebar that is 18 inches long.
To construct a hoop house, start by placing steel rebar 6 inches into the ground at a 35-degree or 45-degree angle. If leaving rebar in the ground, make it noticeable by either painting, placing flags, or using rebar caps to prevent tripping hazards. Place rebar 3 to 4 feet apart in rows parallel to one another. Using 8-foot sections of PVC pipe, place one end of the pipe over the rebar, bend the pipe and place the other end of the pipe over the rebar directly across, creating a hoop. Continue to place rebar and PVC every 4 to 5 feet apart in a row.
PVC pipes have shorter lifespans than metal hoops.
You will need 10-foot metal hoops (known as Quick Hoops) and a metal hoop bender for this project.
To construct metal hoops, bend them into a half circle using a hoop bender to make sure they are all the same. Depending on the style of metal hoop bender you use, you can create different widths to cover one or more rows. Place the hoops 5 to 6 inches into the ground, spacing them 5 feet apart in a row.
An additional top rail of pipe connecting the bows can be added to reinforce the metal hoops.
The best width for a low tunnel hoop is 4 feet, since this width efficiently covers a 4-foot-wide raised bed, leaving 2 feet on either side for accessibility.
. You will need the following materials: 16-foot livestock panels and landscaping pins or rebar stakes.
Secure one end of your wire panel into the ground with landscaping pins or rebar stakes, then bend the panel to your desired shape. To secure the other end, you may need reinforcement if you want a taller tunnel.
Low Tunnel Row Covers
Agriculture floating row covers are available in different grades to protect against frost, heavy freezes, and pests. You will need to decide on your plan with your low tunnel and purchase the appropriate grade row covers. A major advantage of using hoops with row covers is that it keeps the weight of the snowfall off your crops.
This is a way to extend your season by using row covers. A row cover is a type ofblanket that is placed over the hoops of a garden bed to extend the growing season. The row cover isSecured tightly to the hoops to prevent it from blowing away or being crushed by snow. The row cover can be secured with snaps or clips, or by using objects like bricks, rocks, or sandbags. If you’re just overwintering crops and not harvesting, you can secure the cover more permanently by burying the sides or weighing it down with heavier objects.
To protect plants from cold weather, use a row cover. For extra protection in cold temperatures, use a second layer of row cover or a heavier weight row cover. In the winter, place a layer of 4-mil or 6-mil agriculture-grade plastic over the row cover and secure it so that snow can slide off. On warmer, sunny days, lift the sides of the plastic to ventilate the tunnel and avoid overheating the plants. Low tunnel clips can be used to secure the lifted sides of the hoops. The plastic can cause moisture build-up inside the tunnel, so use it only as needed.
You can remove the row covers when it’s sunny and the temperature is above 55 degrees Fahrenheit for cool-season crops, but you may need to put them back on in the evening and overnight when the temperature drops into the 30s.
Closely monitoring outside temperatures on a daily basis is the most important thing you can do to manage the heat in low tunnels. When temperatures rise close to 30 degrees, you should raise the covers to prevent overheating crops such as lettuce and spinach.
Experience is the best teacher for knowing when and how much covers need to be lifted based on factors such as plastic thickness, the intensity of the sun, specific crop requirements, and day length.
Some days you will need to open the entire cover, while other days may only require ventilation on the sides or ends.
A way to determine your needs is to stick your hand into the tunnel without lifting the cover to feel the inside temperature. Thermometers are also helpful and only require a quick glance.
At the end of the day, close the tunnel to trap heat inside. This will help keep the temperature warm during the night.
This text is about how low tunnels can extend the gardening season. Low tunnels are cheap and easy to make, and they can give you an earlier harvest or a later one. With a little bit of effort, you can have fresh, homegrown produce for Christmas dinner or for early in the season.
Just remember to be creative, and enjoy the journey!
Sidebar: Extra Insulation
I use a combination of low tunnels, covered with a heavy blanket of leaves, to extend my season by a couple of weeks. When you’re faced with extreme weather, you may need extra insulation for your low tunnels temporarily. In my garden, for example, I use a combination of low tunnels covered with a heavy blanket of leaves to extend my season by a couple of weeks.
I usually use sheets with a 3-mil thickness for the very end of spring, and I prefer 6 mils for extra-early gardening or gardening into winter.
I add more layers of plastic sheeting to the low tunnel to temporarily increase insulation as needed, and remove them once the harsh weather passes by. Some years, I’ve even added bed sheets when I ran out of plastic. Again, creativity goes a long way with low tunnels, so use what you have in an emergency.