The Black locust tree (species name: Robinia pseudoacacia) is native to the southeastern United States but is widely planted in other regions as an urban ornamental tree. It is also grown as a honey plant in some countries.
The flower of the Black locust tree is a loose hanging "raceme" inflorescence. The individual flowers have a "papilionaceous" (butterfly like) shape (see image below). In Spain these flowers are sometimes called "pan y quesito" (bread and cheese) in reference to the fact that the flowers are edible. To give them a try all you have to do is pluck the petals from the flower base and nibble on the soft, sweet base of the petals. Some have even made a syrup from this sweet nectar.
The leaf arrangement of the Black locust tree is parallel, compound and odd-pinnate with the individual leaves having an "ovate" to slightly "obcordate" (heart) shape.
The Black locust is also a thorn tree although from my observations the twin thorns grow mainly on the "epicormic shoots". These are the shoots that grow from the base or trunk of the tree from an epicormic bud below the surface of the bark. The normal branches do not seem to have many thorns at all.