Quercus x filialis (Q. phellos x velutina) hybrid oak Fagaceae QUXFI; R, pr (planted), ro; Quercus filialis.oaks of the world free.fr. (Accessed 9/2014) Quercus x filialis is a tree, in the red oak group, possibly only one or two left in NYC. Leaves narrow with variable lobes . Flowers monoecious. males in cakins, females 1 to several together. Fruit acorns.