CLOCHES, COLD FRAMES, GLASSHOUSES, POLYTUNNELS & HOTBEDS
2. Cold Frames
3. Glasshouses & Polytunnels
So, let’s start with cloches, because they are the easiest and cheapest and also very useful. Their usefulness as temporary protection for tender seedlings in the spring has been covered in: ‘PROPAGATION TECHNIQUES’ – in the section – HARDENING-OFF & PLANTING OUT.
Long Cloches: used to be made of glass, but now are usually low polythene tunnels stretched over metal hoops and held down at the ends. These are useful to warm the soil in late winter, early spring and cover rows of plants, simply using a corrugated clear plastic sheet bent over and held in place with pegs or sticks. It is also a good idea to place a sheet of plastic to cover each end.
The other type of long plastic cloche (or grow tunnel) is made of polythene sheeting stretched over galvanised metal hoops and held down with wires. I make my own with 2.5mm hard-drawn wire turned on a jig.
Single Plant Cloches: can be bought or homemade. We use 5 litre (1 gallon) spring water or juice bottles with the bottoms cut off and the caps taken off to place over newly planted-out seedlings at night until they have settled in, but they need a bamboo pushed through the top into the soil to stop them blowing over. Plastic bell cloches can also be bought, which have holes around the rim to peg them down.
2. COLD FRAMES
Cold frames are not often known about, but I think they are a very valuable addition to any garden or community garden. They are in fact a small glasshouse, very useful for starting seedlings, striking cuttings, hardening-off young plants and growing salad crops directly in the soil through the winter.
The body can be made of wood, or more permanent ones made of brick or concrete blocks. You can use old window frames with the glass in for the lights (lids), but they won’t last long because the rain cannot run off properly. You will see from the photo and the drawing how the glass at the lower end, overlaps the bottom strut, allowing the water to run off, thus reducing the inevitable rot on the bottom rung.
The lights can be made of a simple frame with a clear polyethylene cover stretched over the frame. As long as the lights are on a slight slop the water will run off. In colder areas a brick or block cold frame can be half buried in the ground for extra warmth and protection.
3. GLASSHOUSES & POLYTUNNELS
Even here in Nelson, we have a small lean-to greenhouse and a cold frame to start our early seedlings in, and homemade cloches to protect early crops planted outside, until they get established. The glasshouse is also used to grow turmeric and ginger in, as well as early tomatoes. In colder areas it is even more important to have a glasshouse for protection, or even a cold frame and cloches, the whole purpose being to extend the growing season.
For community gardens, for those selling produce, or those living in intentional communities – glasshouses and/or Polytunnels are a must. The ventilation of Polytunnels are more problematic, but with many types you can role up the sides in hot weather and open the door for ventilation. Also Polytunnels are plastic, which in the long run degrades. However at this point in time they are useful structures.
In warmer areas with mild winters hotbeds are not necessary, but in colder areas and countries, this traditional way of growing winter and early spring crops is certainly worth considering. Hotbeds work by using the heat of rotting manure to grow a range of vegetables in cold weather. This was the method we used on our farm in the UK for early crops like salads, spinach, early young carrots and early zucchini crops.
To build a hot bed, you will have to obtain a good load of fresh horse manure, preferably mixed with bedding straw. Otherwise mix in at least twice as much spray-free straw as manure + some autumn leaves you have saved if possible. Pile up in a rectangular heap about 60cm (2ft) deep, and allow it to heat up. The heap should be around 30cm (12in) wider and longer than the wooden cold frame you will be using on top. The straw and/or leaves will slow the heating process down and make it last longer.
The heap could easily reach 600C (1400F) and then start to cool down. Level off the top and evenly apply 15cm (6in) of one part sieved topsoil mixed with one part well rotted garden compost. It is important to make sure the heap has reached a warm but not hot state, before sowing or planting into the topsoil and closing the lights.
With early crops like zucchini, they will continue to produce after the heat has gone out of the manure, because by that time the roots will have reached the manure and continue to grow well through the summer with the frames off. One can also grow very early seedlings to be hardened off and planted out later in spring.