Don't know what species but almost all Melocactus are highly tropical, not happy below 5C and really best above 10C.

aajoo, you wrote:

..... can some of you tell me the species? Do you think it could survive through the winter in a cold greenhouse?

You know the deal in naming even mature Melocactus -- so many intermediary and varietal forms -- it is not always easy. As in this case: could be a form of M. curvispinus or M. bahiensis or M. acunai ..... and so on. A better defined (more mature) cephalium, close up of multiple flowers and especially fruit will help a lot for attribution.

It all depends how you define "cold greenhouse" -- cold survival can be "iffy" and unpredictable -- S&B has it right -- visit my Brazilian cacti pages for detailed information.

James

Darn it! I can't even type the correct URL for my own Web pages anymore! Here is the correction:

Brazilian cacti pages

James

Thank SnB and James. From your answers I guess it is better to keep my Melo in a sunny place into my house just through the coldiest months of winter when we can have few cold days (0-5 °C)
Davide