Cold Frame Gardening | What Is It, and Why You Should Try It

If you are looking for a foolproof way to extend your gardening season, reduce pests, and increase your harvest in a Northern climate, cold frame gardening is your best option.

Many gardening tips and guides assume you have perfect soil, no weeds, and the ideal climate, but in reality many of us have to deal with sudden temperature changes and other unforeseen circumstances such as storms, and pests that we may not be prepared for.

Indoor windowsill gardening is a great way to avoid many of these issues, but there is an easy way to protect your hard work outdoors as well. Today I'm going to teach you how even a first time gardener can be successful using an age old technique ideal for beating frost and unexpected cold weather.

Some of the links in this post lead to affiliate sites through which Earth, Food, and Fire may earn a small commission should you make a purchase. For more info check the Affiliate Disclaimer.  All advice, and opinions are based on observations from my own garden.

What Is A Cold Frame?

A cold frame is very similar to a raised garden bed, (and a raised garden bed can actually be turned into a cold frame). The difference between the two is that a cold frame has a clear lid of some sort and sometimes some insulation. Cold frames can be constructed from very basic items, such as four straw bales placed in a box like shape with an old window or even clear plastic sheeting laid over top as a cover.

Or, they can be complex structures, built out of wood, with a heat activated hinged lid which automatically opens when the temperature inside rises too high. You could easily turn an existing raised garden bed into a cold frame by attaching a lid to to it. The key is that the lid will allow sunlight to enter the box, warming the trapped air in the cold frame.

Benefits Of Using A Cold Frame

A cold frame is simple to use, and you can garden in it just like you would a raised garden bed. The benefits of using a cold frame in your garden are many:

• You can extend the gardening season by as much as 60 days (depending on your location), by planting earlier in the Spring and letting a Fall crop grow later into the winter.
• Can be used to start and harden off seedlings before the normal gardening season begins.
• The vegetables planted inside a cold frame are protected from the elements, such as heavy winds, rain, cold, and most importantly frost.
• Bugs and insects have a harder time getting at your crop, producing vegetables and greens that look prettier and have less damage.
• A cold frame will allow cold hardy crops to grow virtually all year round if you insulate the cold frame before winter with straw bales on the outside. It can also be used to over winter tender plants that may not otherwise survive a harsh winter.

What To Grow In Your Cold Frame

You can pretty well grow anything you would like in a cold frame, but there are certain vegetables that will benefit much more from this warm, sheltered space than others.

Some plants such as tomatoes, cucumbers, and garlic will grow too large for a cold frame. One option for these tall growing vegetables would be to use a portable cold frame or one with a removable lid to protect the young seedlings from frost. Later in the growing season when all danger of frost has passed the cold frame can be converted into a raised style garden bed.

If you plan to use a cold frame to start seeds early for plants such as cucumbers, squash, and beans, remember, that they will eventually need to be transplanted out of the cold frame. For this reason, I start my seedlings in small pots, and simply 'store' them in the cold frame until I can transplant the seedlings to a more permanent location in the garden.

The vegetables and greens that will really benefit the most from cold frame gardening are:

• Lettuces & other Greens - especially cold hardy greens such as kale and spinach.
• Delicate herbs - such as parsley
• Root vegetables such as beets, radishes, and carrots
• Brassicas such as broccoli, and cauliflower
• Scallions and leeks

Extending The Growing Season

I tend to grow lettuces and herbs in my cold frame in the early spring to get a jump on the growing season and benefit from growing my own produce sooner.  Here in Prince Edward Island where the growing season is fairly short, I get away with planting lettuce in early May, a whole month before I would start planting in a traditional garden.

This is extremely useful, since the fast growing lettuce quickly matures, allowing for a second planting and harvest before I transition to warm weather vegetables by the end of June/beginning of July.

Even throughout the warmer summer months when my cold frame acts as more of a raised garden bed and is filled with tomatoes, basil, etc, I use the shade provided by the tomato vines to keep growing small amounts of lettuce greens, to provide me a year long supply.

Come the end of summer, when the fruit bearing plants are beginning to ripen the last of their crop, I start to sow root vegetables such as carrots and beets, which will mature just before winter. As you can see I overlap the planting so that there is always something growing in the cold frame

Tips For Cold Frame Gardening

You will be surprised at the quality and ease with which vegetables will grow in this magic garden box! That being said, there are a few things to know and keep in mind to make your cold frame successful.

Properly Fertilize and Mulch

Once you have planted in your cold frame it can be difficult to apply fertilizer and manure, since plants are closer together. Ensure that the soil is very well amended before you start growing. Mulch in between the planted rows, with straw or newspaper helps to keep weeds to a minimum. out what amendments you need and what role they play in this guide to using fertilizer and compost by Redawna Kalynchuk.

Regular watering

Since the cold frame is covered by a lid, your plants will not receive any water from rain. This means that you have to water the cold frame (in my experience) every day! It is best to do this in the morning to give the plants something to drink throughout the day. Since the cold frame is also generally warmer than the outside temperature, moisture will evaporate faster. Consider setting up a drip irrigation system coupled with a mechanical watering timer to allow for regular daily watering.

Plant in rows and weed regularly

Planting your crops in tight rows has the benefit of being able to grow more crops in a smaller space. Plant shade loving or fast growing plants among taller and slower growing vegetables to maximize your harvest. Be sure to weed anything that sprouts outside of the designated rows to reduce competition for nutrients and allow your plants to flourish.

Don't fill the cold frame completely with soil

Make sure to leave at the very least a good foot or two of head space between the soil level and the lid. The plants need room to grow and adequate air movement to develop in a healthy fashion. This air pocket is what will allow the cold frame to function properly. When the lid is closed sunlight will warm the trapped air, raising the temperature two to four degrees above the 'outside' temperature.

Check the weather forecast

Make sure you know what weather is headed your way so you can prepare accordingly. Close the lid and fasten it if need be for strong storms, or prop open the lid when warmer than usual weather is expected. If you have a wooden cold frame, consider painting it white on the outside to reflect sunlight and reduce overheating in the early summer months.

I hope you consider cold frame gardening in your own backyard vegetable garden. It has completely changed how I plan my garden and allows me to enjoy fresh produce longer! There are many things you can do to increase your gardens productivity, and gardening in a cold frame is probably one of the easiest!

Comment below if you have or are thing about using a cold frame garden at home! If you do use a cold frame, take a picture and tag me on Facebook & Instagram: @earthfoodandfire . 

Some of the links in this post lead to affiliate sites through which Earth, Food, and Fire may earn a small commission should you make a purchase. For more info check the Affiliate Disclaimer.  All advice, and opinions are based on  observations in my own garden.