The Mexican White Oak of the Botanic Garden

Quercus polymorpha barely counts as a North American oak. Its range runs through Mexico, Guatemala and Honduras, and it crosses into the United States only once, in a single wild stand roughly 30 kilometres north of the Rio Grande in Texas. Everywhere else it grows, it grows on purpose: gardeners prize it for holding its leaves through most of a mild winter and for shrugging off heat that would strip a European oak bare. The regional register lists Valencia's specimen as the Alzina de Mexic del Botanic, girth 3.44 metres and a crown 25.2 metres across, nearly as wide as the tree is tall at 26.5 metres. That crown is doing the work here: this is a garden oak built for shade rather than height, a wide flat canopy over one of the botanic garden's paths. Nobody has dated it, and no second source beyond the regional catalogue has turned up to confirm the measurements, though that catalogue is the same body responsible for every monumental and singular tree the region records. If you know when it was planted, or have stood under it, tell us. It grows in the university's botanic garden, the same paid-entry collection as the Silk Floss Tree and the Virginia Oak nearby.