nice dendrograms !!
http://gastonsanchez.com/blog/how-to/2012/10/03/Dendrograms.html
also change font size
# example from ?hclust
hc <- hclust(dist(USArrests), "ave")
# default label size
plot(hc, xlab="xlab", ylab="ylab", main="main", sub="")
# reduced label size
par(cex=0.3, mar=c(5, 8, 4, 1))
plot(hc, xlab="", ylab="", main="", sub="", axes=FALSE)
par(cex=1)
title(xlab="xlab", ylab="ylab", main="main")
axis(2)