There are over seven million trees in the Big Apple by the USDA’s count, but only around 120 worthy of the NYC Parks Department's official title “Great Tree of New York City.” These are trees of historical, botanical or cultural significance, with five of them located within the Brooklyn Botanic Garden. One of these, located on the west side of the garden, is a Caucasian Wingnut ( Pterocarya fraxinifolia ) – a giant, gnarled and wizened specimen with a trunk that splits into four parts, one so thick and horizontal that it needs external help in the form of a crutch to stay up.  The tree originally came from Rome in 1922 as a sapling, and in its century of growth has achieved 60 feet in height and nine feet in diameter. The tree was propagated in 1978, with the younger tree planted further down the path near the Herb Garden. The original has seen its share of rough years and bears some scars, but the core of it is still healthy despite the precarious appearance of some of its branches.…