A Putative Hybrid between Phoradendron juniperinum and P. capitellatum (Viscaceae) from Northern Arizona

Juniper mistletoe (Phoradendron juniperinum, Viscaceae) and hairy mistletoe (P. capitellatum) commonly parasitize junipers (Juniperus spp.) in Arizona. Although hybridization between species of Phoradendron is rare, this note reports the occurrence of a putative hybrid between these mistletoes in northern Arizona. The principal characteristics of the hybrid plant are the length, width, and pubescence of leaves, which are intermediate between the parent species. The putative hybrid is a female plant, and although it flowered and formed 17 fruits in 2017, seeds from the mature fruits did not germinate, suggesting that the hybrid is probably sterile.