A New Fabric Pull

I managed to sneak in some sewing time recently and, despite having many projects waiting for some finishing touches, I now have a new wall hanging that I'm starting to work towards.  I started by pulling these fabrics from my collection:

And now I need to figure out how to make some trees.  I made a test block this weekend but was not impressed with how it turned out.  The method I attempted will need some adjusting and I'm not convinced it's the way to go.

So now I'd like to put the question to my visitors!  Does anyone have a favorite (and hopefully easy) method to make an isosceles triangle in a square that they would care to share?

Linking up to W.i.P. Wednesday.