How many trees do you decorate?

Have you gotten your Christmas tree up already? When I was a child, the first weekend in December was the time we set aside to decorate the Christmas tree. I have carried on the same tradition with my husband, but this year we have been a bit late because of the circumstances. We are borrowing my parents' tree, because we thought it was silly to buy a new one for just one year, and because in Italy it is very hard (and expensive) to find real trees. 

We thus decorated one tree, and placed it in the living room. Lately, I have read at least few accounts about the fact that there can be multiple trees in the same house. In the apartment where we are living this year there would not be enough space for more than one tree, but I have to confess that even in our big house in Canada I never thought about decorating more than one tree.

So I am curious: how many trees do you decorate?