[R] rotating an hclust tree with negative hights

[Vahid Partovi Nia]

Hi,
I have an hclust object say hcl  with heights starting from a negative 
and ending to a positive value.

I would like to rotate the plot(hcl) 90 degrees clockwise.

It is suggested to use plot(as.dendogram(hcl), horiz=T) but I 
encountered two problems:
1) a dendrogram object does not accept negative heights
2) horiz=T rotates the tree 90 degrees unclockwise

any ideas?
thanks,
Vahid PARTOVI NIA.