I don't know of a Italian clematis website, but there is a very nice forum with many international posters. Maybe there is someone from Italy who could help you with your soil question.

gardenbuddies.com

Alcenero,

Benvenuto. La sabbia dovrebbe essere piu tosto grossolano. In Inglese si chiama qualcosa come "sabbia appuntita" o "sharp sand". Non so il nome in Italiano. Per fare tagli, uso 100% perlite, ma lo tengo sempre umido.

Conosco i siti di sotto in Italiano. Buona fortuna; puo farmi un email se ha altre domande, sopratutto di clematidi.

http://www.compagniadelgiardinaggio.it/

http://www.fioriweb.it/

http://groups.google.it/group/it.hobby.giardinaggio/topics?hl=it&lnk=sg

http://www.funghiitaliani.it/

Wow, Michael, that is fantastic!

Everyone's generosity is what always keeps me coming back to GW

Thank you Michael and Janetpiole,

the site gardenbuddies.com is well done.
While waiting for an answer i found two italian websites, digilander.libero.it/clematidi and www.clematidi.it
The first very clear and simple with some beautiful photos.
In the second, the photos was not very nice, but it seems well made (I mean the articles).
Among other things, in the links section of this last web site, i found this forum and the web reccomended by Janetpiole.

Thanks again.