Our most frequently asked question has to be “Are your pots frost proof?” and we’re happy to advise.
The answer can be quite complicated but it is also, in a way, very simple. Nothing can be said to be completely frost proof but many pots and planters are, to a certain extent, frost resistant.
For a start, as you can see in our photographs and at The Pot Place, we don’t mind leaving our pots outside. If they’re well drained, they should survive a Cumbrian winter with no problems. However most pots, regardless of the materials they’re made of, are likely to crack if filled with water and allowed to freeze.
Beyond that, it’s all about how they’re made.
Ceramic pots can be made of many different types of clay and fired to a variety of temperatures. The firing temperature and the type of clay determine how frost resistant the resulting pot will be. All pots, whatever they’re made of, must be cared for and kept well drained. This means ensuring that they’re kept slightly off the ground using pot feet or small stones and keeping the drainage holes in the base of the pot free from obstruction. These simple precautions are good for your pots and also good for your plants!
The three most common types of clay used for garden pots and their properties are described below. Pots can also be glazed or unglazed and, contrary to popular belief, the glaze is not always relevant when deciding how durable your pot will be over the winter months.
- Terracotta pots These are usually various shades of orange in colour, normally unglazed and often the cheapest type of pot you can buy. They are also notoriously the most vulnerable pots in winter. Terracotta clay, when fired to its normal temperature of about 1080 degrees C, is still porous and it’s not possible to fire terracotta to a point where it becomes totally non-porous. Because of this, all untreated terracotta pots are prone to damage from frost. The most common problem is a result of water soaking into the surface of the pot and then freezing. This causes the gradual flaking of the surface and eventual destruction of the pot. However, by treating the pot with a sealant, you can avoid some of this porosity and prolong the life by several years. It’s possible to have a terracotta-coloured pot which, through a combination of types of clay, firing duration, initial water content and a good shape, is virtually frost proof.
- Earthenware Pots These pots are the next step up from terracotta in terms of how high they are fired (normally between 1100 and 1200 degrees C.) The fired pot in its unglazed state is quite a light cream or buff colour and they are generally less porous than terracotta and therefore more durable in the winter. Earthenware pots can be unglazed but are normally glazed and the temperature of firing allows them to be glazed with quite bright colours that would not be possible on stoneware pots (see below). The only problem with some of them is that as they can still be slightly porous on the unglazed surfaces so the body of the pot may still absorb water (usually from the inside surface) and be vulnerable to frost. The glaze on these pots can sometimes blow out or flake off under harsh winter conditions too but, again, keeping the pot well drained at all times will help prolong its life.
- Stoneware and Saltglaze Pots These are the highest temperature fired pots normally found in a garden and they are fired to around 1280 degrees C. At this point, these types of clays become vitrified, which means that the particles of the clay bond together in such a way that water molecules are too big to be absorbed into the pot. Just as silica or sand can be heated to form glass, this type of clay can also be fired to form a waterproof material. These types of pot are normally quite dark in colour and they can be glazed or unglazed. Even the unglazed pots are waterproof, making them the most durable type of ceramic pot for your garden.
Of course, not all containers used in the garden are made from ceramics – and we have some in our selection that might look like one material but are actually something completely different!
And whether or not a container is frost proof may not always be a relevant question. Many containers are over wintered in a greenhouse or conservatory or the plants they contain may be annuals which are replaced every year, allowing you to empty the pot for the winter months.
Whatever you choose, at The Pot Place, we try to ensure that all the containers we sell are of the highest quality, suitable for their intended use in a Cumbrian garden and that any precautions you need to take to look after them are clearly explained to you before purchase. We want you to enjoy your pots and planters and to come back to us again in future too.
Our friendly team are happy to advise you on the suitability of a particular pot for the plants and the position that you have in mind, so please feel free to ask.