Cold Frame Gardening: Your Own Mini Greenhouse

Ashley Patterson and one of her cold frames in her backyard garden.

Ashley Patterson and one of her cold frames in her Salt Lake City backyard garden.

By Lizzi Brosseau

Growing Cold Weather Crops with Prefab Cold Frames

Gardening in Utah doesn’t only mean summer tomatoes. If you wish you could eat fresh from the garden all year long, using a cold frame for winter gardening could be the answer to all your fresh eating dreams! 

Cold frames are a popular DIY garden project, but if you don’t have the time or know-how to make a cold frame of your own, do not despair. Any gardener can continue to eat fresh food straight from your garden all year long with the help of prefabricated cold frames. Easy to use and maintain prefab cold frames can create a greenhouse environment that extends the growing season for cold weather favorites, like salad greens, beets, carrots and onions. 

We visited Ashley Patterson’s backyard garden for a closer look at her prefab cold frames. Ashley is the Executive Director of Wasatch Community Gardens, and an avid home gardener. We came back with great information and tips about growing your own fresh food, even in the winter!


Video: Ashley Patterson’s Cold Frames


What is a cold frame?

A cold frame at its simplest is a bottomless box placed over garden beds to insulate plants from inclement weather. They are made of transparent panels that allow sunlight in, and often have a hinged top that can be opened and closed to modify the inside temperature of the cold frame.

Even though their name suggests that cold frames are for cold temperatures, they can actually be used in any season. They are most often used to protect growing plants from the cold, wind and frost in spring and fall, however, cold frames can also be used in the summer to create microclimates for plants that are better suited for more mild zones than Utah’s.

Cold frames in Ashley Patterson’s backyard garden. These cold frames are made of lightweight and easy-to-move polycarbonate.

 

DIY Cold Frame vs. Prefab Cold Frame

Cold frames are a very popular DIY project, because the idea behind them is pretty simple. A home gardener could use any number of at-hand materials to construct a cold frame: old windows, gardening cover, sheets of transparent plastic or glass, wood planks, bricks, and screen materials. All of these can be used to make a DIY cold frame, or other cover structures, like low-tunnels or hoop houses. 

If you’d like to learn more about hoop houses, check out our hoop house and low-tunnel blog post: https://www.pbsutah.org/modern-gardener/stories/how-to-build-hoop-houses

In Ashley Patterson’s garden, she opted to buy a pre-fabricated cold frame, rather than embarking on a DIY project. One reason for that is DIY cold frames are often bulky and difficult to store. The materials of Ashley’s prefab cold frame are light, easy to assemble, and easy to put back into the shed.

Ashley’s cold frames are manufactured by Juwel and are available in a few sizes and options. The sides and lids are made of lightweight, clear polycarbonate, with an aluminum frame, plastic brackets and metal pins and screws. The polycarbonate is coated with a no-drip coating to prevent heavy condensation. 

With this information about the differences between DIY and prefab cold frames in your garden tool belt, let’s talk about what plants can be grown in a cold frame next!

Kale, lettuce and spinach thriving in Ashley’s cold frame on a clear day in December.

 

What Grows Best in a Cold Frame?

Ok, you’re excited about extending your gardening season so that you can have fresh veggies to eat during wintertime, so let’s get into what veggies you could grow in a cold frame.

When it comes to choosing what plants to grow in a cold frame, the first consideration is the size of the plant. Crops that vine out or grow tall are not suitable for most cold frames, simply because they won’t fit in the cold frame. Keep the height of your cold frame in mind when planning your winter garden.

The hardiness of the plant is the next consideration. Cool weather crops are what you’ll see most people using their cold frames to grow.

Here’s a short list of cool weather crops to get you inspired: 

  • Winter lettuces
  • Scallions
  • Kale
  • Arugula
  • Carrots
  • Bok choy
  • Mizuna
  • Mustard
  • Spinach
  • Radish
  • Lettuce 
  • Endive

These plants are hardy and will grow throughout a typical Utah winter under the protection of a cold frame. See this article for a detailed list of cold hardy plants!

Ashley is a huge fan of succession planting and uses her cold frames to succession plant arugula for fresh salads throughout the winter.

 

Although cold frames are most often used for half-hardy and hardy plants that thrive in cooler temperatures, don’t rule out using a cold frame to help warm season crops too.

As an example of using a cold frame on warm season crops, Ashley showed us how she used cold frames to extend the life of a basil plant and an eggplant that were adjacent to beds that she had been preparing for winter growing. These warm season plants wouldn’t survive in a cold frame over winter, but because she had strategically planted them next to her winter beds, she was able to include them in her cold frame placement, protecting them from the early frost we had this year.

Ashley had other great tips for gardening in a cold frame, which we’ll share next.

 

Ashley proudly showing off the salad greens in her cold frame garden.

4 Tips From Ashley for Successful Cold Frame Gardening

Since Ashley has had her cold frames for 15 years, and she’s a gardener by profession, she’s a great resource for inside information about cold frame gardening. Here are some of her top tips for getting the most out of your cold frame:

  1. Succession plant, succession plant, succession plant. Ashley is a big fan of succession planting in her cold frames, especially since most cold weather plants grow relatively quickly, are easy to harvest, and take little space. That makes cold frame gardening the perfect place for succession planting. 

     

  2. Cold frames can be extra helpful if you have pest issues. Another benefit of having a cold frame is that it can act as a physical barrier between your plants and pests like insects, birds, mice and cats. 

     

  3. Move your cold frame! If you have a lot of gardening to do in your cold frame, pick it up and get it out of the way so that your work is easier. Ashley’s prefab cold frames make that very easy, because the materials it is made from are so light. 

     

  4. Put your cold frame away when it won’t be used. Don’t leave it out in the sun or it may start to yellow and deteriorate. Ashley has had her cold frames for 15 years and believes that they’ve held up so well because she puts them in the garage over the summer. 

Ashley takes off and vertically stacks the lids from her cold frames.

 

Making the Most of Your Winter Garden 

We hope these tips and information about prefab cold frames have been inspiring, and that you feel ready to start your own winter salad bar for keeping fresh veggies on your dinner table all year long! 

Don’t forget to follow Modern Gardener on Instagram and Facebook to see more information about gardening, and make sure to chime in with your own tips or stories! We love to learn from other gardeners, and look forward to seeing what you’re learning in the garden too!

If you live in Utah and have a garden or garden project that you'd like to be featured on Modern Gardener, click here!

Lizzi Brosseau

Lizzi Brosseau, Digital Producer at KUED Channel 7.
Modern Gardener Host and Author

Lizzi works for PBS Utah as a digital producer and host of Modern Gardener. Read more