Advice on temperature

Hello. I could really do with some advice on temperature for my collection of Mammillaria.
I live on the west coast of Scotland and the weather is unpredictable to say the least!
My cacti are currently housed in a cold greenhouse for much of the year but I tend to bring
them into the house during the Winter. My question is: what temperatures can they cope with?
Would it be safe to leave them in the greenhouse over winter?

Hi,
Glad you made it here. I'm moving this thread to the "General Question" section as it might get more replies.

I think that to get a good answer, it would be helpful to know the temperature range you might experience, as the answer to your question as it stands is "it depends!". Not many Mamms are frost hardy, at least not on a continuing basis. They would need to be totally dry in their pots, and even then I wouldn't trust many much below 5C.

If you look at the Mesa Garden seed list online at http://www.mesagarden.com/c2015.html you will see after the species name some numbers and slashes. On their home page at http://www.mesagarden.com/ quite a way down there is a section called cultivation tips. That has the key to what the numbers mean and numbers 14-18 deal with temperature minima.