When we think of gardening, it’s common to conjure up images of summer and all those juicy summer crops we love so much. However, these images prevent us from realizing a year-round garden. The reality is that there are people who live in climates where it’s freezing much of the year but successfully grow during much of that time. It takes a little infrastructure, but you can have fresh food throughout the cold months. Start here with season extension basics.

What is Season Extension?

Simply put, season extension describes methods you can use to extend the season. It’s not limited to winter gardening. A walipini, for example, is an underground greenhouse designed to protect crops from intense heat. For this article, though, we are focusing on season extension methods typically used to grow crops through colder climates.

Different Types of Cold Season Extension

The most common forms of winter protection—besides greenhouses—are cold frames, row cover, low tunnels, and high tunnels. Cold frames are either a raised bed or set in the ground. What makes these spaces a cold frame is the clear lid that angles towards the sun covering the growing area. High tunnels (also referred to as hoop houses), low tunnels, & row covers are half-circle, tunnel-like structures covered with crop protective material.

High tunnels are sized so that multiple beds fit underneath and are usually tall enough to walk through. Low tunnels are tunnel structures that cover a single bed and typically range from two to four feet high. Row cover tunnels are tunnels that cover just a single row in a bed.


In greenhouse construction, the clear materials used to cover the greenhouse are typically glass or polycarbonate hard plastics and referred to as glazes. Cold frames are typically raised beds,  made of wood, sometimes insulated, and topped with an angled glass or plexi-glass. 

For hoop houses of all sizes, the materials used to cover the hoop house area are generally known as coverings. These coverings are either agricultural fabric or flexible plastic and come in different thicknesses. The thicker the covering, the more protection. But thicker does not necessarily mean better. The thicker the covering, the less light your plants receive. So ideally, you want to make sure that your greenhouse is in an area that will get 8-10 hours of sunlight so your plants don’t lose too much sunlight from whatever covering you have on your hoop house. 

The type of season extension you’ll need depends on how cold your winter temperatures get. If you have mild winters and you want to grow just cold hardy crops, you might only need a row cover with a light agricultural fabric covering. If you live in a climate with a harsh winter, you might choose a row cover with a thick agricultural fabric and a low tunnel or hoop house with a medium to thick flexible plastic covering. There’s so much more to season extension that you’ll want to know before finalizing your infrastructure plans, but these season extension basics can get you started on your winter garden journey.

Want to discover more about season extension and learn how to grow a winter garden? Check out the Winter Gardening Course.