The Crenate Oak of the Botanical Garden

This oak is two species at once. Quercus crenata is the natural hybrid of the Turkey oak and the cork oak, and Italian calls it cerro-sughera after both parents in turn. It appears wherever the two grow within pollen range of each other, it is never common, and it does not breed true, so most specimens are one-offs rather than a population. You can read the parentage off the tree. The bark thickens and cracks into something approaching the cork oak's spongy layer, never quite as deep, but soft enough to press a thumb into. The leaves settle the question: shallow rounded teeth all around the margin, which is what crenata describes, and a habit of hanging on through the winter instead of dropping cleanly, so from December to March the tree is half evergreen and looks undecided about it. At 440 centimetres round and 18 metres it is one of the widest trunks the registers record inside this garden. Both of them list it and neither can agree what to call it. The national register writes Quercus crenata, the regional one writes Quercus hispanica, which is the older umbrella name for crosses between the same two parents. An argument about what to call a hybrid is roughly the argument a hybrid deserves.