Salt build up from fertilizers used.

Or simply lime in the water, we never use fertiliser on our alpines Bathgate but the pots regularly get like this. Soak the pots for a good 24 hours, Bulba puts our into the rain butt on a piece of rope, this will soften the deposit the start scrubbing with a pan scourer but not a metal one... Unlikely you'll get it all off but, unless you are putting the pot and its plant on a show bench, no one worries too much.

I agree, soaking is probably the best way to remove the salt/lime deposits. Totally submerge the pots under water for a good 48 hours. Too much scrubbing could cause it to crack. I wouldn't worry about it too much.

Using a scrubby sponge soaked in white vinegar wipe down the outside of the pot then rinse with water.

Thanks guys. Soak in tapwater or rainwater? My waterbut is empty at the mo btw. I quite like a bit of character on my pots but just want to some off so when it builds up again I don't end up with a white pot instead of terracotta! Thank you for your help.

You can always paint them

Wouldn't consider painting an unglazed terracotta pot Bathgate... If you have no rain water it will have to be tap water but allow to stand for 24 hours before you start soaking the pots in. A scrubby sponge with white vinegar ca certainly help Loosestrife but if you soak first most of the deposit comes away a lot easier.

I wasn't talking to you Mg. My comment was for Amsterdam. Painting is certainly a viable option. Acrylic paints are the way to go. You can get stamping tools or just go to town.

Given that one of the important things about an unglazed terracotta pot is that it breaths then Amsterdam needs to br aware of this before he goes painting them.

It's an option Mg. The world isn't coming to an end. She's a smart lady.

Rain water is preferable as it is slightly acidic whereas tap water will have been neuteralised at the water works.

thanks all for your suggestions and opinions! I will soak in tap water after it has stood for 24 hours. Now need to find container big enough.....

Btw Moongrowe I am of the female persuasion!

Right I'll remember that Amsterdam :) At least, I hope I will...

If you do a vinegar wipe down with a hose rinse it's going to go alot faster and you won't have to use your bathtub to soak your largest pots.

Thanks Loosestrife2.