I think the saddest tree in Winter is the pin oak. Holding onto its leaves for dear life seemingly, it is encased in a shroud of dried, dirty brown leaves until the Spring.
It, like most oaks as well as beeches and hornbeams, retains its leaves because of marcescence. A simple way to describe this characteristic is most deciduous trees drop their leaves in Fall by forming a protective layer where the leaf is attached to a branch. Oaks and similar trees don’t but rather drop their leaves in the Spring when leaf buds swell and push off the old growth. Nobody knows why; there are many theories.
Perhaps a backdrop of pure white snow rescues the aesthetic of pin oaks in Winter, but we don’t have that now as its current coat melts into the background of fallen leaves that have long since left their perches on high.
