The London plane, "Platanus" × "acerifolia", is a hybrid or a cultivar. Exactly what the parents were in uncertain. It was extensively planted on London streets before WWII, but is no longer in favour. The London plane is very tolerant of air pollution and root compaction (small space for roots). For these reasons it was a popular urban roadside tree. Now, however, it is indirectly something of a pest. Aphids in their millions suck sap from its leaves, and drop sugary liquid onto cars parked underneath. Older London streets have virtually no off-road parking.