When it comes to growing in the garden, winter always seems to sneak upon us! The refreshing air of October quickly turns into the nippy air of December, and many crops do not like this change. There is nothing like fresh salads, radishes, and kale during the cool fall and winter months. But how can we grow them with frosts on the way? We all would love a greenhouse, but they are frequently too expensive to consider for home gardening. And cold frames while they work are cumbersome and challenging to set up. Today, we will look at another option to protect crops year-round – how to make low tunnels.
Low tunnels are essentially tunnels that are built low to the ground. Anywhere between 12-30 inches from the top to the ground. They offer similar advantages as greenhouses by lifting the frost off the plant and on the fabric covering. But with the disadvantage that you can not work standing up in the structure. A smaller air mass also cools down quicker versus a larger air mass, but the ease to set up and inexpensive aspects of how to make low tunnels make them an excellent choice. Depending on the covering, it can also boost the air and soil temperature, which works wonders for maintaining a garden during the cooler months of the year. There are different designs to choose from for constructing and particular crops that especially thrive in this environment.
Note: This post may contain affiliate links. We earn a small commission at no additional cost to you. Read our disclaimer for more details.
Why low tunnels?
So why low tunnels? One of the first things that led me to use low tunnels is how inexpensive they are to construct. Rather than spending hundreds or even thousands of dollars for a high tunnel, low tunnels can be constructed for less than 1/30th the cost! Do take note, a low tunnel does not allow you to walk inside to work as a high tunnel does. But it does effectively provide a covering for the crops. A low tunnel brings these savings as the focus is to shed the wind rather than having to brace against it as you would with a taller structure. This means that a 9 gauge wire is substantial enough to hold the fabric versus steel tubing.
Secondly, it is easy to learn how to make low tunnels yourself. For my first low tunnel, the only tools I needed were a wire cutter, 9 gauge wire and a little time. Since 9 gauge wire comes in a spool, there is already a semi-circle shape in the memory of the wire. We use this to our advantage by bending the wire in the direction of that circular format to span the beds. Once you have the length of the wire determined and 1 wire cut, that wire can be used for the template to cut the rest of the wires. Using this process can make covering a 3’X40’ bed fast, easy, and fun.
A low tunnel also effectively raises your growing environment under the tunnel by one growing zone! For example, if you live in zone 7b, it increases this to 8a. This is equivalent to a 5 degree difference for your plants! It may not always register 5 degrees warmer at night under a low tunnel, but the solar energy it captures during the day warms up the air and soil significantly to have the effect of 5 degrees. I have used this effectively to grow beautiful radishes, lettuce, arugula, and kohlrabi all through the winter.
Low tunnels are also completely temporary and easy to store for seasonal use. Rather than having a permanent structure, all that you need to do to put a low tunnel away is pick up the hoops, roll up the fabric, and store for the following season. This flexibility makes winter growing feasible without sacrificing space to a permanent structure.
Lastly, low tunnels can serve multiple purposes. If you live in the south as we do, you have probably experienced how challenging it can be to grow squash in the summer. Whether it is vine borers or pickle worms, bugs love squash! By planting the squash under a low tunnel, however, gives us the option to cover the crops at night with agribon or insect netting. This prevents moths from laying their eggs on the plant and can help extend the harvest season.
You can also find out more about the seasonal extension at our blog post Protect your garden from frost.
Supply List
Here are the tools that I found to be very helpful for creating low tunnels:
- 9 gauge wire
- Wire cutters
- Agribon (aka frost cover)
You will also need something to weight the covering down. I frequently use bricks that are around the homestead but anything that is heavy works great.
How to make low tunnels
Making low tunnels is fun, easy and fast. And a great project to get the whole family involved. For the first hoop, I like to start on a flat piece of ground near the garden. To begin, you first need to determine what type of crop you would like to cover. Broccoli, for instance, take up much more space and are taller than lettuce plants. For this purpose, it can be helpful to cut different size hoops to cover the height of the crop desired to be covered.
When calculating, it is important to support the fabric so that it does not touch the surface of the leaf plant. Since agribon works by lifting the frost off from the plants, if the frosted fabric touches a leaf it will suffer frost burn. Frost burn is often worse than a standard frost, as the constant contact enables the cell walls of a leaf to drop to a much lower temperature. If in doubt, make it a bit taller.
For our hoops, we have standardized the size to fit the majority of our crops. As we figured out how to make low tunnels for our beds, the length that worked for us was xx inches. To cut the wire, I like to have the coil of wire still inside of 1 of the straps that holds it together. This helps prevent kinking of the 9 gauge wire while also keeping it contained rather than springing all over the field.
Step-by-Step
Step 1. Determine the height of the desired crop to be covered
Step 2. Measure the width of the bed to be covered
Step 3. Cut the wire to span the bed and have enough height to cover the crops
Step 4. Place wire 4 inches into ground spaced 4 feet apart
Step 5. Cross 2 hoops at each end of the bed to support the cross tension of the fabric weight
Step 6. Cover the hoops with the fabric of choice
Step 7. Place weights (bricks or sandbags work great) every-other hoop along the length
Step 8. Enjoy salads all year long!
Standard Wire Lengths
| Width of bed | 30″ | 36″ | 40″ |
| Heigh of crop | 12″ – 16″ – 20″ | 12″ – 16″ – 20″ | 12″ – 16″ – 20″ |
| Length of wire | 48″ – 53″ – 59″ | 52″ – 58″ – 64″ | 58″ – 62″ – 67″ |
Conclusion
I hope you found that learning how to make low tunnels is quick and inspiring to grow throughout the cold winter months. And may many fresh winter salads grace your plates for many seasons to come!
