What is a Coldframe

Even the smallest garden can benefit from a coldframe and in fact it is sometimes in the smallest gardens where the coldframe comes into its own.

Some gardeners use coldframes as mini greenhouses, especially when they don’t have the space or the budget for a full size glasshouse.
Other gardeners that have the luxury of a greenhouse use a coldframe as an interim stage between the greenhouse and the garden.
Either way the humble coldframe is an invaluable part of the garden kit and fulfils many essential needs.

The term coldframe refers to the fact that most garden coldframes are unheated.
They rely on the energy of solar radiation to harness some warmth that is so essential in the colder months of the year, but the frame itself also performs some vital weather protection.
While it would generally be inefficient to heat a coldframe in the winter and many would consider this to be a waste of energy there are circumstances when it is possible to add a heat source and bring on plants, seedlings and cuttings ahead of the season.
To do this your coldframe needs to be well insulated from beneath and in a sheltered position.
An ideal heat source would be a soil warming cable positioned beneath the plants in a bed of sand, this could be regulated by a thermostat but would need a professionally installed electrical supply.
Unless you have precious plants that can’t be over wintered elsewhere or you have a structured growing schedule that requires extending the season, it may not be cost effective and is unlikely to be very eco friendly to heat a coldframe.
Ideally, a sectioned off area of an unheated greenhouse would be a better solution, or perhaps you have space in a spare room, utility room or a house porch that will benefit from some of the heat from your home.
A coldframe will still provide the essential halfway house before your plants are ready to plant outside and you will get the benefit from saving money and extending the season at both ends.

When the garden only has room for a coldframe it is essential to buy the very best you can afford. There are many flimsy, first coldframes, that to be honest are better reserved for the kids garden.
If you want a coldframe that performs efficiently then invest in the best.

Look for top quality materials. Western Red Cedar framed coldframes are better insulated that other timber coldframes and those framed with aluminium.
Look for toughened safety glass, an absolute essential when the coldframe is at ground level and accessible by children, pets and wildlife.
Consider the ventilation. In the winter the plants still need an airflow, but in the heat of the summer the internal coldframe environment can quickly reach levels too hot for many plants. An integrated system that allows the coldframe to be ventilated at different levels is an essential part of coldframe gardening. Make sure that the lid can be securely propped open at different levels, is resistant to wind damage and can be removed easily when required.
The rear height of the coldframe needs to be tall enough to accommodate a range of difference plants and to allow them to grow taller.

Ideally you need to place your coldframe into an area where it is protected from violent weather, against a wall or a fence is ideal.
Don’t forget that coldframes do not need to be ground hugging, they can also be an upright, patio house that has removable shelves to accommodate your plants as they grow.
Do your research carefully, choose a top quality model that will last the lifetime of your garden and use it to extend the growing season and to save yourself money on plants and cuttings. For a great choice of garden coldframes check out what’s on offer at Gabriel Ash.

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