UBC Botanical Garden's Eric La Fountaine contributed both today's photographs and the write-up. Eric writes:
I became quite enamored with the impressive structure and shiny deep green bipinnately compound leaves of this tree on my recent visit to Hawaii. It can be seen in many locations in the island chain. Samanea saman (PDF) (synonym Albizia saman) is a native of central and northern South America, but is grown in many tropical regions and is a very popular tree in the Pacific. Its large umbrella-shaped canopy makes it a wonderful shade tree. It is sometimes planted to provide shade for coffee plantations.
The trees can grow quite large, attaining heights of 30 meters or more with a dense low spreading crown to almost the same dimension. Like some other members of the legume family, the leaves fold at night and on cloudy days, possibly one of the reasons for its common name of rain tree. A good collection of photos showing form can be seen on Plants of Hawaii.