h1, h2 are handles which means you can use them to automagically or manually change properties of the plot. For example:
z = magic(5);
[h1,t1,perm1] = dendrogram(ceil(rand(10,3)*10));
%it's blue; Yuck!
%Make it Red, Yay!
set(h1,'color','red')
I used set to take the handle and change one of the properites associated with it.
doc set
doc get
etc.
