How To Make A Cold Frame For Hardening Off Your Plants

April is a time when many of us who have been sowing and growing on our windowsills will be considering getting seedlings ready for the rest of their lives outside. While the date we move certain types of plant outdoors will vary depending on the conditions those plants thrive in and where we live in the UK, for many of us, we will experience our last frost date before the end of the month. Even in gardens that lie further north, there are plenty of hardier plants that can begin their journey to their final growing positions.


By Ofer El-HashaharA cold frame will make the process of acclimatising seedlings to outdoors conditions far easier. But in order to acquire this useful piece of garden equipment, you do not need to buy one expensively. It is fairly easy to make your own cold frame using inexpensive reclaimed materials which can often be found online or at a local reclamation yard. A cold frame does not have to be enormous and so can find a space even in smaller gardens. It should be placed close to the house, ideally between the door you use most often to carry plants out of the house and the area where your plants are eventually to grow. A well planned garden design will make your life a lot easier.


The first stage in constructing a cold frame is to find/buy a piece of glazing to make the lid of your cold frame. This lid will be raised or lowered to expose plants to the breeze while still giving them a little bit of protection. An old window is ideal – though if you have children or dogs running around then it could be a good idea to find some old safety glass, as accidents can happen. The size of this old window will determine the eventual size of your cold frame.


The cold frame will be rectangular in shape, but remember, it should slope down towards the front, ideally facing south, certainly in fullBy Arpent Nourricier sun. Measure your new lid and determine the size of the rectangular base that you will have to make. There are a number of ways to make the base from materials you may have easy access to. Bricks can make a very sturdy cold frame but the easiest and cheapest option is probably to construct a simple frame from reclaimed timber. Wood is relatively easy to work with and you will need only rudimentary woodworking skills. You will need some wood (e.g. old stud timber) for the framing and some planks to make the sides of your cold frame. Inexpensive metal corner brackets will strengthen the structure if required. You can choose to nail or screw. You will need some hinges and a stick that will hold up the lid at a couple of different heights when you want it open. Decide on your exact design before you begin.


When you have all the measurements, your design plan and materials to hand, you can start the assembly. Begin by creating the base and sides, then fit the sloping top frame to which your lid will be attached. The whole thing will then be strengthened by adding your planks to the sides, front and back. If you have been working somewhere other than the final location for your cold frame, it may be an idea to move the frame before cladding it as it will gain a lot of weight and be harder to move after this next stage. When your cold frame base is finished, you can hinge on your lid and you are ready to furnish your cold frame and harden off your plants.

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