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 (affiliate) which automatically opens when the temperature inside rises to 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 which 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 past 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, 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 through out 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 of 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.Find out what amendments you need and what role they play in this guide to using fertilizer and compost by Redawna Kalynchuk.
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 (affiliate) coupled with a mechanical watering timer (affiliate) 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 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.
Do you need to plant in a cold frame in Southern CA? San Diego area to be exact? If I am planting red yucca seeds to they need regular watering - is the soil supposed to stay moist all the time?
Chef Markus Mueller
Hi Nancy, If you need a cold frame will depend on your temperature. A cold frame is meant to protect from freezing temperatures in winter. I have never grown red yucca, as it is not native to Eastern Canada, so I can't really comment on specifics for that plant, but after doing a quick google search for red yucca I see that it grows to a height of 4-6 feet. A cold frame is only ever a few feet high, so this plant is likely not suited for one anyway.
I m trying my cold frame for the first time and I was wondering if you know where and which thermostat I can put in my cold frame to monitor the heat.
Chef Markus Mueller
Hi Cécélia, I don't have a thermometer in my cold frame, though i suppose you could simply go an purchase a refrigerator thermometer and hang it inside. Keep in mind opening the frame would cause the temperature reading to fluctuate though, especially in winter. If you can find a digital one with a remote display that would probably be ideal.
This is super interesting! I'm new to gardening and started up my first container garden this spring and am seeing just how much of a labor of love it is. But it's great. I'm storing this knowledge for when I have a backyard garden one day. I've seen plenty of raised garden beds, but never with a lid.
Today I learned!
A cold frame is a great way to protect from garden pests! My husband planted some lettuce and radishes in a small cold frame early this spring. As the weather grew warmer, he lifted it away. It was lovely to be able to harvest early salad ingredients. I like the automation provided by that hinge and drip irrigation system!
While I can't lift mine away completly, I'll be removing the lid and using it as a raised bed! The drip irrigation is a cool idea eh! I havn't done it myself but next year, I'm going to try and hook it up to my rain barrel!
Amanda (Peppers & Pennies)
What an interesting contraption! I think my neighbour down the street has on of these on wheels and I never quite knew what was going on, but now it makes sense! We live near a wooded area in the city that is by a golf course, two rivers and park land so we have a ton of bunnies and white tailed deer who love to nibble.
I always appreciate your educational posts. Opens my eyes up to a lot of things I could/should be doing to be more of a homesteader!
This ia my first go at a cold frame, but I am already surprised at how well it has worked! If if you obly have a small one with one or two things in it, its worth it!