Cold Frame Gardening: Getting Started
Excerpted from: The Starter’s Guide to Using Cold Frame in Gardening
Imagine if you can have a fresh green salad in February or some juicy red tomatoes in November.
Sounds like a dream doesn’t it? Maybe you’ve heard of it. Maybe you’ve seen it. It's cold frame gardening.
Yes. All of this can happen in your very own garden. And you don’t even need a lot of space for this.
So for your convenience, we have gathered the most important and basic info you will need about
cold frame gardening.
Cold frame gardening is a form of planting different types of green life in an enclosed environment
with the aim of extending the growing season of the plants. Building a cold frame is not a hard task.
All you need is to make a wooden panel frame from an old glass window and put the glass over the
The ideal place is a sunny, south-facing spot that has good drainage and also offers at least some
protection from the wind and other elements. Ideally, it should get full sun from mid-morning to
Before setting up a cold frame in a permanent place, it’s best to dig down 6-10 inches and amend the
soil with compost and organic matter to help drainage if your soil is heavy clay like mine is. It’s important
that your cold frames have adequate drainage to keep your plants healthy.
The key to success is to pay close attention to the temperature – it should be under 75 degrees in the
cold frame for summer plants, and below 60 degrees for plants that typically grow in the spring or fall.
If you need to achieve a cooler temperature, lift the lid to let air in.
Many gardeners follow this general rule: if the temperature outside is over 40 degrees, keep the lid
open about six inches, when they top 50 degrees, take the lid off altogether, but be sure to replace it
in late afternoon in order to trap enough heat in for cool nights.
On nights where temps dip below freezing, your plants in the cold frame will likely need some extra
protection, you can do this by adding insulation on top of the lid – newspaper, straw, old blankets or
whatever you happen to have handy should work.
The whole idea of the cold frame’s structure is to protect the plants from the harsh conditions of
late autumn, winter, and early spring. It shelters the green life from snow, rain, strong winds, hail
and ice. Thanks to the window roof it also collects sunlight and warmth, keeping them inside the
frame for a longer time. A cold frame structure usually keeps a difference of 5 to 10 degrees between
the inside and outside environment.
You place the seeds inside the frame and they grow into plants, resistant to the cold weather. Still,
the collected heat needs to escape in order not to fry out your crops. The best thing you can do is
to install a vent with a closing mechanism. Opening it every two days would be enough.
The cold frame is perfect if you want to harden young plants. To harden them means to acclimatize
them to harsher weather conditions, higher or lower humidity and increased air movement before it’s
time to plant them outside. The cold frame will serve as the middle stage when you are transferring the
plants from inside your house to the garden. The frame is a controlled environment so you can use it
however you need.
Using the cold frame in the summer allows you to provide certain plants with more heat before the
season actually starts. This is very useful when planting, for example, tomatoes and chillies. The
increased warmth from the cold frame will encourage and speed up their growth.
Another use for it during summer will be propagating plants. No surprise heat waves or rainy days
will be able to interrupt your gardening plans when you are using the cold frame. You can start from
seeds, semi-ripe cuttings or young plants and adjust the conditions according to the needs of your crops.
In the autumn cold frames will protect the young plants and cuttings from unpredicted weather conditions
like early snow or night frosts. You will also be able to extend your harvest season with at least 4 weeks.
You can use your cold frame in winter to prevent alpines from rotting by shielding them from the rain and
snow. You can overwinter the fresh annuals and keep them until spring comes. If you want to add some
extra protection, you can place a layer of bubble plastic on the inside. It will protect the plants from frosts
but it will reduce the light and ventilation as well.
Thankfully, cold frames are also easy and inexpensive to build! There are many plans available to choose from.
Also, there are a number of commercially available kits if you're busy or not the DIY-type.