We live in the land of the Washingtonias and it is really hard to distinguish young robustas from filiferas, let alone identify hybrids, without knowing where they are from or having a lot of experience. They are very similar plants in any case, the only two species in the genus. Native to dry Baja California and surrounding areas, found in arroyos, canyons and washes.
Washingtonias account for most of the palms in cultivation in Southern California and Baja California, especially street trees. They will naturalize and seed a pretty wide area, hybridizing freely. Birds will drop seeds at quite a distance.
The plants pictured are quite close together by my standards. W. robusta will grow a much wider base in old age, often invading concrete and walls in the process.
Washingtonia in habitat here.
