Growing under glass offers us the opportunity to expand the variety and type of plants we want to grow. In the UK, our weather can be unpredictable at the best of times.
A greenhouse creates a more stable growing environment so that tender seedlings and half-hardy or non-hardy plants can proliferate and thrive.
A coldframe or cloche is, by and large, an extension of your average unheated greenhouse.
This article explores how and why gardeners use coldframes and cloches.
The Difference Between a Coldframe and a Cloche
Coldframes and Cloches basically serve the same purpose. Both provide tender plants, cuttings and seedlings with protection from the elements, namely wind, rain and freezing ground or air temperatures. Because frost and snow in particular can wither and destroy plant cells, a coldframe or cloche is vitally important in acting as a barrier that mediates the air temperature inside the structure.
Coldframes tend to be unheated, and one of their main uses is to acclimatise and eventually harden off cuttings and seedlings – a sort of halfway house between the greenhouse and being planted directly outside. coldframes are also great for over-wintering potted plants.
Cloches can be constructed from different materials, depending on their intended use. For instance, tunnel cloches are often made from thermal fleece or polythene (for protecting tender plants from frost and windchill), and act much in the same way as a mini polytunnel. However, you can also buy cloches made from special micro gauze or mesh with the sole intention of protecting your crops from damaging pests and diseases. Cloches also tend to be mobile, as they’re often placed over crops of vegetables and removed once the risk of frost has passed.
Some cloches, such as the Victorian-style ‘bell cloche’, can be used to protect smaller areas – for instance, if you have a specific half-hardy flower or shrub. These types of cloche tend to be constructed from plastic resins, glass or Perspex and are often decorative in style.
Where to Site Your Coldframe
It’s important that your coldframe is sited in the right place, especially if constructing a permanent brick-based structure. You will need to site the coldframe in an area that gets a fair amount of sunlight, so that the air circulating within the frame has a chance to heat up. Bear in mind that wooden-framed coldframes can deteriorate much quicker in damp, shady spots too.
Ideally a coldframe will be situated against a wall away from prevailing winds – usually close to the greenhouse, outbuildings or close to the house. If your greenhouse or external wall is heated from the inside, this will also add extra warmth to the coldframe. Likewise, sinking the coldframe down into the soil will also help to insulate it.
The site for your coldframe should also have good drainage, to avoid damp, waterlogging and rot. If your coldframe is built or placed directly onto earth, you can aid drainage by putting down a layer of shingle, slates or old smashed crockery. You can also add a slight incline to the angle of the earth so that excess water is able to drain away more easily.
Tips for Using Your Coldframe and Cloche
One extremely pertinent piece of advice in regards to using your coldframe or cloche is to make sure that it has enough ventilation. A plethora of problems can arise from damp, most usually fungal-like and disease-ridden in nature! Most shop-bought coldframes are designed so that their lids or ‘roof’ can be propped open during warmer weather. If designing your own coldframe, this is something that you must bear in mind. The same ethos applies to cloches, particularly those that use plastic covers – ventilation is key to successful growing.
Some coldframes are heated and as such, it might be easier to regulate temperature. However, the majority are unheated, so it’s up to you to act swiftly if temperatures are threatening to fry or freeze your plants. In spring, summer and early autumn, if using your coldframe you will need to make sure that it’s not in direct sunlight all day if the temperatures are set to rise. You should also make sure that the lid is open so that air can easily circulate. Likewise, in winter, a too-shady spot will no doubt prove to be a frost pocket, and your plants can suffer as a consequence. If you’re worried that your coldframe won’t provide enough protection during cold snaps, you can always bolster it by padding it out with thermal fleece, blankets, wool or straw.
A coldframe or cloche makes an ideal addition to any garden enthusiast’s garden. If well-built, properly sited and well-regulated, your coldframe will extend your growing season by a matter of months each year.