Quercus rugosa x macrocarpa | Stanford
This is another Netleaf Oak (Q. rugosa) hybrid sourced from the Shields Grove, growing in yet another new oak test zone at Stanford Unviersity. The pollen parent, again, appears to be Bur Oak (Q. macrocarpa), judging from the enlarged sinuses. This tree is growing strongly but moderately in size. The leaf habit of this tree is semi-evergreen, losing about half of its leaves over the course of the winter. Netleaf Oak and its hybrids are typically identified by the great leaf thickness - far greater than any native oak from California, or the rest of the continental United States. The example of Netleaf Oak hybrids shown here speak to the immense range of variation possible with oaks from arboreta, or other mixed oak, settings. Netleaf Oak proves particularly susceptible to variation, due to the fact that the tree, at least in Davis, is in flower for an extended period of time, thus being exposed to a wide range of pollen from the different reproductively compatible oaks present in the Shields Grove, with the pollen-dispensing catkins appearing on different species at different time, exposing the Netleaf Oak flowers to different oak pollen, depending on timing.