Extend Your Growing Season with Cold Frames for Raised Garden Beds

Gardening is a rewarding hobby that allows you to grow your own fresh produce and enjoy the beauty of nature right in your backyard. However, the growing season can be short, especially in colder climates. That’s where cold frames come in – they provide an easy and affordable way to extend your growing season and protect your plants from the elements. In this article, we’ll explore the benefits of using cold frames for raised garden beds and share some tips on how to get started.

What are Cold Frames?

A cold frame is a simple structure that acts as a miniature greenhouse for your garden. It’s typically made of a transparent material, such as glass or plastic, with a frame that can be opened or closed to regulate the temperature and ventilation inside. Cold frames are designed to capture and retain heat from the sun, creating a warm and protected environment for your plants.

Why Use Cold Frames for Raised Garden Beds?

Using cold frames with raised garden beds offers several advantages:

  1. Extend the Growing Season: Cold frames allow you to start planting earlier in the spring and continue growing later into the fall. By trapping the sun’s warmth and protecting your plants from frost and cold winds, you can extend your growing season by several weeks or even months.

  2. Protect Tender Plants: Some plants, such as tomatoes, peppers, and herbs, are sensitive to cold temperatures. Cold frames provide a sheltered environment for these tender plants, allowing you to grow them even when the outside temperatures are less than ideal.

  3. Maximize Space: Raised garden beds are an efficient way to maximize your growing space, and adding a cold frame on top takes advantage of vertical space as well. This is particularly useful for urban gardeners or those with limited outdoor space.

  4. Conserve Water: The enclosed environment of a cold frame helps to retain moisture, reducing the need for frequent watering.

  5. Pest Control: Cold frames can also help to keep pests, such as insects and small animals, away from your plants.

Types of Cold Frames

There are several types of cold frames to choose from, each with its own advantages:

Permanent Cold Frames

These are sturdy structures, often made of wood or metal, that are designed to be left in place year-round. They are more expensive than temporary cold frames but offer better insulation and protection for your plants.

Temporary Cold Frames

Temporary cold frames are lightweight and portable, making them easy to move around your garden as needed. They are typically made of plastic or fiberglass and can be disassembled and stored when not in use.

Raised Bed Cold Frames

As the name suggests, raised bed cold frames are designed specifically for use with raised garden beds. They are typically made of durable materials like powder-coated steel and PVC, and they can be easily attached to the raised bed frame.

Building Your Own Cold Frame

If you’re handy with tools, you can build your own cold frame for your raised garden bed. Here are some basic steps to follow:

  1. Choose Your Materials: You’ll need a sturdy frame (wood or metal), a transparent cover (glass, plastic, or polycarbonate), and hinges or a mechanism to open and close the lid.

  2. Determine the Size: Measure your raised garden bed and build the cold frame to fit snugly on top.

  3. Construct the Frame: Assemble the frame using your chosen materials, ensuring it’s sturdy and level.

  4. Add the Transparent Cover: Attach the transparent cover to the frame, using hinges or a sliding mechanism to allow for easy access.

  5. Consider Ventilation: Include vents or a way to prop open the lid for ventilation on warmer days.

  6. Insulate (Optional): For added protection, you can insulate the sides and bottom of the cold frame with materials like styrofoam or bubble wrap.

Alternatively, you can purchase a pre-made cold frame kit designed specifically for raised garden beds, which can save you time and effort.

Using Your Cold Frame

Once you’ve set up your cold frame on your raised garden bed, it’s time to start using it effectively:

  • Seedlings and Transplants: Cold frames are perfect for starting seedlings or hardening off transplants before moving them to the outdoor garden.
  • Season Extension: In early spring, gradually open the cold frame lid on warm days to allow your plants to acclimate to the outdoor conditions. In the fall, close the lid to protect your plants from frost and extend the growing season.
  • Ventilation: On sunny days, be sure to open the vents or prop open the lid to prevent overheating and ensure proper air circulation.
  • Watering: Check soil moisture levels regularly and water as needed, but be careful not to overwater in the enclosed environment.
  • Monitor Temperatures: Use a thermometer to track the temperature inside the cold frame and make adjustments as necessary.

Tips for Successful Cold Frame Gardening

To get the most out of your cold frame and raised garden bed setup, keep these tips in mind:

  • Orientation: Position your cold frame to maximize sun exposure, typically facing south or southeast.
  • Insulation: Add extra insulation, such as straw bales or bubble wrap, around the sides and bottom of the cold frame for extra protection on cold nights.
  • Automatic Vents: Consider installing automatic vents or a temperature-controlled opener to regulate the temperature without manual intervention.
  • Crop Selection: Choose cold-hardy crops like lettuce, spinach, kale, and root vegetables for fall and winter growing in your cold frame.
  • Maintenance: Keep the transparent cover clean and free from dirt and debris to maximize light transmission.


Cold frames are a simple and cost-effective way to extend your growing season and protect your plants in raised garden beds. By creating a warm and sheltered environment, you can start planting earlier in the spring and continue harvesting well into the fall or even winter. Whether you build your own cold frame or purchase a pre-made kit, this gardening tool is a valuable addition to any backyard vegetable garden or raised bed setup.



Can you put a cold frame on a raised bed?

Protect your plants from frost with a simple cold frame that sits right on top of your existing 4′ x 4′ raised bed. The lid is held open with screen door closers, and the entire frame can be moved easily when the weather warms up. Cut the lumber yourself, or have the boards pre-cut at your local home improvement store.

When should I start using a cold frame?

For warm-season plants, I wait until the temperatures have stabilized and we are within two to three weeks of our last frost date. In general, wait until seedlings have formed multiple sets of true leaves and are well rooted before moving them into cold frames.

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