Sorbus × hybrida by thrushes and waxwings, which disperse the seeds. It is a tetraploid species of hybrid origin between "S. aucuparia" (European rowan) and "S. intermedia" (Swedish whitebeam), the latter being a tetraploid triple hybrid between "S. aucuparia", "S. torminalis", and either "S. aria" or one of its close relatives. "S. intermedia" differs from "S. hybrida" in having the leaves less deeply lobed with no separate leaflets. Closely related "Sorbus meinichii" is a triploid or tetraploid species of hybrid origin between "S. hybrida" and "S. aucuparia" and differs in having the basal four to six pairs of lobes cut right to the
North Fork Mountain pine barren in the Central Appalachians. Other rocky summits, including the summit of Pike Knob, are blanketed by red pine ("Pinus resinosa") forests, here at their southernmost natural occurrences. The Monongahela National Forest has designated of old growth red pine forest on the mountain as the North Fork Mountain Red Pine Botanical Area. Another unusual vegetation type on North Fork Mountain is an elfin forest dominated by yellow birch ("Betula alleghaniensis"), mountain ash ("Sorbus americana"), and mountain holly. The oak-and-pine vegetation of North Fork Mountain contrasts strongly with the more diverse vegetation of the nearby mountains just west of the