Thanks Miss_taken,
I agree with you, it looks like C. perfoliata.
Maybe elongated, but it is under full sun, very strong sun. I would like to grow it more compact but probably this plant is just like that, because I cant give it more sun...
There are different varieties which vary in height. Var. falcata has much broader leaves which are very tightly stacked, clearly not what this is. This is the type shown here - http://davesgarden.com/guides/pf/go/70591/" onclick="window.open(this.href);return false;