Quercus QUSP, Oak. One of the main genus for dendrochronology. There are a lot of species. In northen Europe two are native: Quercus robur and Quercus petraea. Wood samples from the two species are difficult (if possible at all), to distinguish from each other. Usually it is better to label any Quercus chronology as QUSP, rather than as for instance QURO, when more than one specie is available in the area.