Mistletoe is the common name for a group of hemi-parasitic plants in the order Santalales that grow attached to and within the branches of a tree or shrub. Parasitism evolved only nine times in the plant kingdom;[1] of those, the parasitic mistletoe habit has evolved independently five times: Misodendraceae, Loranthaceae, Santalaceae (formerly considered the separate family Eremolepidaceae), and Santalaceae (formerly treated as the separate family Viscaceae). Although Viscaceae and Eremolepidaceae were placed in a broadly-defined Santalaceae by Angiosperm Phylogeny Group 2, DNA data indicates that they evolved independently.[citation needed]

The word 'mistletoe' is of uncertain etymology; it may be related to German Mist, for dung and Tang for branch, since mistletoe can be spread in the feces of birds moving from tree to tree. However, Old English mistel was also used for basil.

European mistletoe, Viscum album, is a poisonous plant that causes acute gastrointestinal problems including stomach pain, and diarrhea along with low pulse.[2]

The name was originally applied to Viscum album (European Mistletoe, Santalaceae), the only species native in Great Britain and much of Europe. Later the name was further extended to other related species, including Phoradendron serotinum (the Eastern Mistletoe of eastern North America, also Santalaceae). European Mistletoe is readily recognized by its smooth-edged oval evergreen leaves borne in pairs along the woody stem, and waxy white berries in dense clusters of 2 to 6. In America, the Eastern Mistletoe is similar, but has shorter, broader leaves and longer clusters of 10 or more berries. In the United States, Phoradendron flavescens is commercially harvested for Christmas decorations.[citation needed]

The largest family of Mistletoes, Loranthaceae, has 73 genera and over 900 species.[3] Subtropical and tropical climates have markedly more Mistletoe species; Australia has 85, of which 71 are in Loranthaceae, and 14 in Santalaceae