Lonely Valley Oak near the intersection of Road F and Trail 15, away from Escobar Gate. April 28, 2009 at 11:05 am. Valley Oak (Quercua lobata) is "winter deciduous" -- it looses its leaves due to changes in light due to the seasons. (Other oaks are "drought deciduous", losing leaves in times of less water.) There are 14 images in this gallery containing this tree -- starting with this one.