This is the famous “Broom Tree” above Henninger Flats.  It is a pine tree with a very strange growth on it.  It was identified by Lillian at the Arboretum as a “Broom”

Here is a close up of the growth.  It appears that mutant branches have morphed into roots and are growing about ten feet above the ground.  It is the only one I’ve ever seen and definitely deserves to be mentioned in any best trees of Pasadena list.