Good Growing

Extend the growing season with low tunnels

Posted: Nov. 12, 2017 12:01 am

One of my favorite times of year to garden is in the fall. Growing vegetables during autumn in Illinois as the weather cools and daylight dwindles can be a bit of a challenge, but the reward is quite sweet.

The fall and winter garden is not a place for tomatoes, peppers or many of our summer veggies. Instead, what we grow are cool-season crops. Adaptation to low temperatures allows most cool-season crops to survive light freezes, while others, such as kale, will tolerate 20 degrees Fahrenheit or lower.

As the weather cools, plants convert carbohydrates into sugars to protect their cells from freezing. This sugary "antifreeze" imparts a deliciously sweet flavor to many cool-season crops. Spinach and carrots harvested in the late fall and winter are especially a treat that one must experience.

Prepping the garden

Preparation is key to cold season growing. In fact, a majority of the work for a fall and winter garden takes place in the summer. Most fall vegetables should be seeded in the ground by early August, but this can vary based on the crop and your location.

The key is to have plants established when we still have ample daylight. In the fall as the days shorten, plant growth slows considerably. Once we hit late fall, plant growth has all but stopped. At that point, we are just maintaining plants harvest.

As an example, late August I seeded carrots. By the time we got to late October, the plants virtually stopped growing due to shorter daylight and were ready for harvest. You could harvest them all at once and store them in the high humidity bin in the fridge for at least one month.

However, I store my carrots where they are growing in the ground through the winter and harvest when I need some.

In our GIFT -- Growing Illinois Food Together -- garden, we are currently growing carrots, spinach, turnips, cabbage, kale, bok choi and various lettuces. The most reliable winter crops in my experience have been kale, carrots and spinach. Contact your local Extension office for additional recommendations of cool season crops.

Holding crops into winter

Another critical part of the fall and winter garden is infrastructure to protect your plants. Yes, these cool-season crops are hardy, but protection is essential if you want to extend your season beyond winter's hard and long frost. The tool for this in the backyard garden is a low tunnel.

Low tunnels are high tunnels (also known as hoop houses) in miniature. To make the low tunnel skeleton that will hold the covering, you may use wire or PVC pipe. However, I strongly recommend purchasing low tunnel materials from dealers who specialize in gardening or small-farm supplies. Some even offer kits with everything you need.

Low tunnels will need to be able to stand up to high winds and snow loads, and often wire and PVC fail.

I made my low tunnel frame using -inch electrical conduit and a pipe bender. Space your hoops five to six feet apart. A rope is then weaved along the top of the hoops and anchored at both ends to a wooden stake in the ground. The rope acts as the "spine" and holds up the low tunnel frame when snow piles on top.

About mid-fall when we get our first light frost, I use row cover, a spun fabric similar to a bedsheet for a light protective covering that lets through sun water and air. Once we approach our first hard frost, I place greenhouse poly plastic covering directly over the row cover. Most homeowners will seek this poly plastic covering from local hardware stores, but plastic drop cloth is not made for use in the garden. Garden and farm suppliers sell low tunnel poly that is treated to protect from UV degradation and will give you a much longer lifespan.

Tie the ends of the row cover or poly covering to the stakes at either end. Use bags of rock or brick to hold down the sides. Keep an eye on the temperature. Sunny, warm winter days can get hot in the low tunnel. Roll up the sides to vent, but don't forget to put them back down before nightfall. Harvest vegetables on days when the temperature is above freezing.

To attain fresh produce in the fall and winter, vegetables have to start growing in mid- to late summer. By mid-fall, most should be ready for harvest. By using a simple season-extension low tunnel, you will be able to hold those vegetables throughout winter and enjoy sugary spinach and candied carrots even after New Year's.

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