Have you ever tried growing lettuce at home only to have most of your crop eaten by bugs, washed out, or be destroyed by a late frost? It can be pretty frustrating putting in all that hard work and not getting any return from it. 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 grow a successful crop of lettuce, by gardening in a cold frame.
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 being that a cold frame has a clear lid of some sort. 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.
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.
- The vegetables planted inside a cold frame are protected from the elements, such as heavy winds, rain, cold, and frost.
- Bugs and insects have a harder time getting at your crop, producing vegetables and greens that look prettier and have less damage.
- Most importantly, 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.
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, grow too large for a cold frame. One option would be to convert it into a raised bed in the summer months, by removing the lid. If you plan to use a cold frame to start seeds early for plants such as cucumbers, squash, and beans, remember, they will need an eventual gardening location outside of the cold frame.
The plants that will really benefit the most out of a cold frame though are:
- Lettuces & Greens
- Delicate herbs
- Root vegetables such as beets, radishes, and carrots
- Brassicas such as broccoli, and cauliflower
- Scallions and leeks
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 end of summer, when the fruit bearing plants are beginning to ripen the last of their crop, I start to sow root vegetables which will mature just before winter. As you can see I overlap the planting so that there is always something growing in the 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.
- Start the growing season in your cold frame, with a healthy dose of compost and manure. Once you have planted in your cold frame it can be difficult to apply fertilizer and manure, since plants are closer together. Therefore ensure that the soil is very well amended and nourished before you start growing. Find out what amendments you need and what role they play in this guide to using fertilizer and compost by Redawna Kalynchuk.
- Do not let your cold frame overheat! If you have cold spells, followed by really warm weather, it is important that you go out and open the lid before the trapped heat kills your plants. If I am leaving for work early, I simply place a wedge(piece of 2×4 or a 4 inch log) under the lid to allow the heat to escape. If you have a wooden cold frame, consider painting it white on the outside to reflect sunlight and reduce overheating in summer months.
- 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 (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. Mulching in between the planted rows, with straw or newspaper helps to keep weeds to a minimum.
- 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.
- Check the weather forecast. Make sure you know what weather is headed your way, to make sure 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.
I hope you consider setting up a cold frame in your own backyard vegetable garden. There are many things you can do to increase your gardens productivity, and gardening in a cold frame, is probably one of the easiest!
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