What to Grow in a Cold Frame

Are you a gardener who wants to push the boundaries of the growing season and get a jumpstart on fresh produce? Look no further than the cold frame that will help you protect your plants from the elements and extend your harvest.

A cold frame is a gardening structure that creates a microclimate to extend the growing season for plants by trapping heat from the sun. If you are keen to have your own mini greenhouse and enjoy fresh produce well into the winter months, read on to find out all about what to grow in a cold frame.

This article discusses cold frames and some top plants you could grow in them for a great harvest.

About Cold Frames

cold frame for gardening

A cold frame is a simple structure used in gardening to extend the growing season by protecting plants from cold temperatures and frost. It typically consists of a bottomless box or frame with a clear cover that allows sunlight in while trapping heat inside. The frame is placed directly on the ground and can be made of various materials, such as wood, metal, or plastic.

A cold frame has a translucent angled top that faces south and gives the plants growing under it the maximum sunlight exposure. Using real glass for the top and sides increases sunlight exposure, and more heat is trapped inside.

The plants can tolerate the toughest weather conditions when grown in a cold frame as the cold frame provides insulation from the cold weather and keeps the soil warm. Cold frames also protect plants from heavy rain and strong winds. If using a cold frame made of plastic, then carefully fix it to the ground so that it doesn’t get blown away.

Cold frames are used to start seedlings earlier in the spring, to protect delicate plants from harsh weather, or to extend the growing season in the fall. They are a cost-effective and easy-to-use solution for gardeners looking to maximize their growing potential.

What Exactly Happens in a Cold Frame?

a cold frame for a garden

Cold frames create a microclimate that is warmer than the surrounding outdoor environment. They work by trapping heat from the sun, which raises the temperature inside the frame and creates a protected environment for plants to grow.

There are cold season crops that grow well during the winter and fall can tolerate even freezing temperatures sometimes. But they don’t like the weather to change from one extreme to the other in a short while, such as a freezing cold night just after a warm sunny day. The cold winds blowing in winter can also damage your plants.

So, a cold frame balances the temperature by trapping heat during the day. This way, it even has warmth during the night and protects the plants from ice, snow, and strong winds.

5 Plants that Grow Best in a Cold Frame

cold frame

Here are 5 plants that you should grow in a cold frame and some of their care and maintenance needs.

1.   Spinach

A cool-weather crop that’s easy to grow and thrives well in a cold frame is spinach. It grows fast, and you can harvest baby spinach leaves in a very short time of just 21 days after planting.

Spinach needs fertile soil, sow seeds with 1-inch gap between them to have the greatest harvest and ¼ inch deep in the soil. It’s good to harvest young baby leaves when the plants become a few inches tall.

2.   Salad Greens

One of the easiest plants to grow in a frame is the salad greens. Like spinach, these vegies grow fast and well in cool weather.

A great thing is that salad greens in a single frame can produce enough salad greens for a family of four all through the winter. To get a continuous fresh supply of salad greens, sow new seeds after two weeks of sowing the previous ones.

For the maximum harvest of salad greens, sow the seeds ¼ inch apart and 1/8 inch deep within the soil.

3.   Scallions/ Baby Onions

Winter soups and roasts are incomplete without a tint of fresh onions. What is better than to have fresh onions straight from the garden? Green onions, scallions, and baby onions all grow very well in cold frames.

If the soil of the frame is rich with nutrients, or you’ve added compost in it, then it will help the bulbs to grow quickly and healthily. Onions can grow from seeds or small bulbs, planted ¼ inch deep in the soil.

4.   Radishes

Having a fresh salad with radishes is a great winter luxury that not everyone can enjoy. Radishes grow fast and very well in a cold frame; you can even harvest some varieties within a month of planting.

If you mix the soil with fresh compost and prepare the soil with nutrients, then radishes will grow better. Sow the radishes ¼ inch deep in fertile, yet ploughed and loose soil.

5.   Kale

 A very healthy and nutritious vegetable which is easy to grow in a cold frame is kale. It comes packed with vitamin C and is considered one of the best antioxidant veggies.

Adding kale to your diet is a very healthy step, and having kale fresh from the garden is an easy way to do this.

Plant kale seeds in soil with 1 inch distance between them, and around 1/8 to ¼ inch deep in the soil. Don’t worry about the cold weather, as actually it improves the flavor of kale.

Other fall and winter vegetables that grow well in a cold frame includes:

  • Leaf lettuce
  • Arugula
  • Beets
  • Kohlrabi
  • Chard
  • Parsley
  • Carrots

Aren’t these all what you need for a healthy salad? If you are having a cold frame garden in an extremely cold place, then do include these very cold-tolerant plants, such as:

  • Endive
  • Mache (corn salad)
  • Claytonia (miner’s lettuce)

Tips For Using a Cold Frame

a cold frame

Here are some tips for growing and maintaining vegetables in a cold frame:

  • Plan and prepare your seeds during summer. Start the plantation in late summer or early fall. This ensures that the plants become stable and mature before extreme weather hits. The crops should be large enough by late November, and then the growth decreases. The purpose of the cold frame is to keep the crops fresh like in a refrigerator till you need to use them and harvest the crops.
  • Watering the plants in cold frames is like watering any other plants. Keep the soil moist, but don’t over-water it, or else the roots will rot. During winters, water the plants less frequently.
  • Don’t put down the cover during the fall, start putting the lid down when night temperatures go to less than 40 F. But even during such times, remember to lift the cover during the daytime, so that the cold frame is properly vented. Proper venting ensures the temperature inside the cold frame remains stabilized.
  • When the winter hits, you do not need to water the plants much. Just take care of venting and harvesting the crops. A tip about harvesting is that it is good to harvest early so that the rest of the crops get space to grow.
  • When you feel that space is freeing up inside the cold frame, then start to plant spring-harvest plants such as spinach and lettuce.
  • Plan for a long fall and winter harvest. But having fresh carrots and radishes in winter salads and soups is a lovely treat.

FAQ’s about Cold Frames

1. What is a cold frame, and how does it work?

A cold frame is a gardening structure that creates a microclimate to extend the growing season for plants by trapping heat from the sun.

2. What are the benefits of using a cold frame for gardening?

The benefits of using a cold frame for gardening include the ability to start plants earlier in the season, protect plants from frost and wind, and extend the growing season into the fall.

3. What materials can be used to build a cold frame?

Materials that can be used to build a cold frame include wood, PVC piping, cinder blocks, bricks, and straw bales.

4. How do I use a cold frame to start seedlings?

To use a cold frame to start seedlings, fill it with soil, plant the seeds, and place a clear lid or plastic sheeting over the top to create a warm, moist environment for the seeds to germinate.

5. Can I grow vegetables in a cold frame, and which ones are best?

Yes, vegetables can be grown in a cold frame, and the best ones to grow are cool season crops like lettuce, spinach, radishes, and carrots.

6. How do I maintain the temperature in my cold frame?

To maintain the temperature in a cold frame, you can open the lid on warm days to release excess heat and close it at night to retain warmth.

7. How do I water plants in a cold frame?

To water plants in a cold frame, use a watering can or hose to water directly into the soil, being careful not to overwater and cause the plants to rot.

8. Can I use a cold frame to overwinter plants?

Yes, you can use a cold frame to overwinter plants, but choose hardy varieties that can withstand cold temperatures and low light levels.

9. How do I protect my plants from pests and diseases in a cold frame?

To protect plants from pests and diseases in a cold frame, keep the frame clean and well-ventilated, and remove any diseased plants or debris promptly.

10. How do I prepare my cold frame for the winter season?

To prepare a cold frame for the winter season, clean out any plant debris, add a layer of fresh compost, and cover with a thick layer of straw or leaves to insulate the soil.

Wrapping Up

Now you know what to grow and how to grow in a cold frame, you can prepare yourself for the next winter season. Plan for your cold frame garden and start planting seeds in late summer or early autumn so that you get a good harvest during the cold days.