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Cold Frames – Uses of Coldframes – Types of Coldframe

Unlike a cloche that moves around the garden, being used for a relatively short period as plants establish or to extend the end of the season, the coldframe is more of a fixed permanent feature in the garden.

Traditional Brick Coldframe

Traditional Brick Coldframe
Large enough for a person to stand inside whilst cultivating

At one time nearly every gardener would have a coldframe. Those without a greenhouse would use their cold frame as a sort of mini-greenhouse and those who had a greenhouse would use their cold frame as an addition and intermediate step to planting out.

In recent years the popularity of coldframes seems to have declined yet they are as immensely useful today as they ever were.

Uses for a Cold Frame

The coldframe serves three main purposes:

  • First it provides a sheltered and relatively warm environment to germinate seeds and bring seedlings on.
  • Second, it provides a sheltered place to grow plants. If you do not have a greenhouse, you can grow cucumbers in a coldframe – hence the name frame cucumbers.
  • Thirdly, the coldframe provides an intermediate stage between greenhouse and planting out in the great outdoors. This process is known as hardening off.

Hardening Off in the Coldframe

If you just take a plant from a nice warm greenhouse and stick it into the cold outside the shock may well kill it and will certainly check growth. The hardening off process introduces the plant to the outside gradually, enabling it to adapt and thrive in the outside world.

Take the plant from the greenhouse and place in the coldframe and open the lid for a few hours in the warmth of the afternoon. After a few days, leave the frame open all through the day, just closing it up at night or if it gets really cold.

By the end of a week to ten days you should be fine to leave the frame open day and night, just sheltering the plants from the worst of the cold. After a fortnight the plant can come out and go into the ground.

Wood Polycarbonate Coldframe

Wood Framed Polycarbonate Coldframe
Very good until the wood warped and the glazing fell out!

Glass Aluminium Coldframe

Aluminium Framed Glass Coldframe
Not recommended where there are children about

Raised Bed Coldframe

Raised Bed Coldframe
Excellent for hardening off etc. but also great for growing very early carrots and potatoes

Types of Cold Frame

There are a number of different types of coldframe.

Traditional Brick Built Coldframe

These were often attached to a greenhouse, coming off a dwarf walled side. They could be most any size from a size we would recognise today to quite large affairs which people could stand inside.

The large ones would often be used as hot beds, being filled with rotting manure and relying on the generated heat to bring on plants.

The Wooden Sided Cold Frame.

This is actually quite easy to build and well within the capabilities of the average person. The wooden sides help keep the warmth of the day in the house overnight and are quite robust. See How to Build a Coldframe

The Aluminium and Glass Cold Frame

This type of coldframe has the advantage of having glass sides, which allows more light to enter, avoiding drawing the plants and spindly stems. The drawback is that they do not hold the heat as well overnight as the wooden sided coldframe. With glass coldframes care should be taken if children are around, glass can be dangerous.

Twin Walled Plastic Cold Frames

Available with wooden or aluminium frames, these are glazed with twin walled polycarbonate. This does not allow as much light through as glass but is far better as an insulator than glass and not as fragile or dangerous if broken. Because the light is diffused by the material, the risk of scorching in sunny weather is reduced.

My experience with a thin wooden framed polycarbonate coldframe is that it warped allowing the glazing panels to spring free.

My Coldframes

I owned a wooden framed polycarbonate coldframe but as I mentioned the frame warped. I have a basic glass sided frame that is very good for hardening off although I have had to replace some panes due to accident. We’ve no little children running around but the cat leaping down from the fence managed to break the glass lights.

I’ve actually got three polycarbonate glazed frames. 2 are upright types, like a glazed cupboard with shelving for seed trays and the third is a coldframe combined with a raised bed base.

This is brilliant for growing very early potatoes and for carrots protecting them from the fly. The potatoes are planted shallowly in the base and this is then earthed up into the deep bed. When the weather warms up the foliage is up to the roof panels, these are removed and stored away. The sides provide enough protection for a shallow frost. Excellent really early crop of potatoes. You can see details of this cold frame in the allotment shop: Cold Frame & Raised Bed

Greenhouse Growing, Coldframes etc. Further information

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