If you’re like us, you are on the hunt for useful, affordable methods of season extension. Congratulations, you found one! Low tunnels are a form of season extension for your market farm. They essentially offer the same advantages as a hoophouse, but at a fraction of the price.

What Are Low Tunnels 

Low tunnels allow for you to have the benefit of a greenhouse without being restricted by where to put them. 

These tunnels are typically used at the beginning and near the end of the growing season. It’s very possible to have your entire production area under the tunnels in the spring when you need the ground warmed up for your starts. 

Low tunnels allow for season extension when you need it, but as summer rolls around and you no longer need to cover your crops, you can take the tunnels off and leave crops in the ground open.

How To Make Low Tunnels

They are made from 10 ft. long galvanized electrical conduit (EMT), bought at your local hardware store and bent into shape using a hoop bender.

This allows the low tunnel hoop to be sturdy enough to handle heavy snow loads.

In early spring and late fall, cover the low tunnels with clear greenhouse film and voila, you have a mini hoophouse.

To hold down row covers, you can bury the edges with dirt, or use sandbags placed at the bottom of the hoops.

Sidenote: If you want your sandbags to last, invest in the UV-treated bags.

When installing a row cover, make sure to stretch it tightly so the fabric does not beat in high winds.

It’s important to check on the low tunnel regularly to make sure the weights are doing their job and your row cover is not being whipped around too much on windy days.

Low Tunnel Challenges

Low tunnels require quite a bit of labour to set up during spring and some labour to maintain as you get snow in the fall.

Your beds must be fully prepared and planted before you cover them up.

Watering beds underneath a low tunnel is a challenge as you must open them at least partially to water them.

Using drip irrigation underneath the tunnel will save you a lot of time at the beginning of the season.

Luckily, when temperatures are cool not a lot of watering is required. However, on days where temps rise, it’s best to open the tunnels up so they can ventilate properly.

It’s important to note that you will need to keep an eye on crops that have a tendency to bolt under stress (bok choy, and radishes). Curtis Stone recommends keeping one end of each tunnel open so they don’t overheat and bolt.

How to Space Low Tunnels

Spacing is especially important in the fall.

If you’re using them for overwinter crops like spinach or carrots, it’s best to leave one bed fallow between your tunnels. 

Once you start to get some snow, if your tunnels are too close together, that snow will build up between the tunnels and force the plastic in enough that it will smother your crop.

By leaving a bed in between, it makes it easier to manage snow as it piles up.

Bottom Line

Low tunnels are a must-have for market farmers. Despite all of the setup, takedown, and upkeep, they are a very valuable and useful form of season extension. 

The early bird gets the worm as they say, and if you use low tunnels, you can get an early start to your growing season and even extend it throughout the winter if you so desire.

If you’re making your own tunnels, make sure to do your research! Much of the information in this article is from J.M. Fortier’s the market gardener and Curtis Stone’s The Urban Farmer. For more information, check our book list here.

We will be making and using our own low tunnels this year, so you can count on some future articles of our experiences making and using them. Stay tuned!

Are you using season extensions on your market farm? Let us know in the comments below.

Stay Local,

Kathy& Jon

your friendly neighbourhood growers