The potting shed
Frost proofing pots
The potting shed
I have bought 2 new terracotta pots, is there any way of frost proofing them?
Hampshire Coast 100m from the sea
Cold, by itself, cannot hurt a pot. But when water freezes it expands and thats what does the damage.
There are two types of damage. If a pot freezes solid, which has wet soil in it. The water will expand and could crack the whole pot. This can happen to any pot - frost-proof or frost-resistant. The solution to this is to not let it get too wet during the winter.
The second effect is when the water soaks into the porous terracotta and expands on freezing. It will chip off bits. The solution is to keep it dry, if possible. You could also seal it - you probably need to do both sides. Any paint or waterproof varnish would do. I have never done it.
By sealing it you are really defeating the idea of using terracotta and might as well use plastic.
"You don't stop gardening because you get old, you get old because you stop gardening." - The Hampshire Hog
At a gardening club I attended the speaker recommended putting pots on feet so not in contact with ground then using polystyrene as crocks and finally putting bubble wrap on the inside of the pots. All help insulation.
west central Scotland
You can minimise it a bit by painting - a layer of pva also helps - but ultimately they will fall apart as H.Hog says.
If you're in a wet/cold area, all you can do is keep the pots sheltered over winter as far as possible. That will depend largely on what you use them for. Grouping them together in cold weather helps a bit as well.
It's a place where beautiful isn't enough of a word....
Vendée, Western France
I use clear acrylic varnish to seal my clay pots. Matt or satin depending on what's available and never more than 3 coats. leave to dry a day between coats, inside and out. It stops moisture penetrating so you don't get the expansion and contraction of ice crystals which is what does for terracotta pots that haven't been fired to a very high (and expensive) degree but it does also stop any patina forming from moss and algae.
Standing on pot feet also helps but the varnish is key.
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
edited March 2019
I bought two pots from a garden centre last year and ask the very same question to someone there. He advise me to buy some water repellent paint (it's clear so don't panic) and paint every part both inside and out, it cost just under £15. I did this left to dry and then potted up my herbs, the two post are still in fine and have been out all winter. Will be doing this with all my pots that need it from now on.