Plant Of The Week: Mistletoe

Mistletoe is the common name for most obligate hemiparasitic plants in the order Santalales. Mistletoes attach to and penetrate the branches of a tree or shrub by a structure called the haustorium, through which they absorb water and nutrients from the host plant.

The name mistletoe originally referred to the species Viscum album (European mistletoe, of the family Santalaceae in the order Santalales); it was the only species native to Great Britain and much of Europe. A separate species, Viscum cruciatum, occurs in Southwest Spain and Southern Portugal, as well as North Africa, Australia and Asia.

Over the centuries, the term has been broadened to include many other species of parasitic plants with similar habits, found in other parts of the world, that are classified in different genera and even families — such as the Misodendraceae and the Loranthaceae.

In particular, the Eastern mistletoe native to North America, Phoradendron leucarpum, belongs to a distinct genus of the Santalaceae family. The genus Viscum is not native to North America, but Viscum album has been introduced to California. European mistletoe has smooth-edged, oval, evergreen leaves borne in pairs along the woody stem, and waxy, white berries that it bears in clusters of two to six. The Eastern mistletoe of North America is similar, but has shorter, broader leaves and longer clusters of 10 or more berries.

The word 'mistletoe' derives from the older form 'mistle', adding the Old English word tān (twig). 'Mistle' is common Germanic (Old High German mistil, Middle High German. mistel, Old English mistel, Old Norse mistil). Further etymology is uncertain, but may be related to the Germanic base for 'mash'.

Parasitism has evolved at least twelve times among the vascular plants; and of those, the parasitic mistletoe habit has evolved independently five times, in the Misodendraceae, Loranthaceae, and Santalaceae, including the former separate families Eremolepidaceae and Viscaceae. Although Viscaceae and Eremolepidaceae were placed in a broadly defined Santalaceae by Angiosperm Phylogeny Group II, DNA data indicate they evolved independently.

The largest family of mistletoes, the Loranthaceae, has 73 genera and over 900 species. Subtropical and tropical climates have markedly more mistletoe species; Australia has 85, of which 71 are in Loranthaceae, and 14 in Santalaceae.

Mistletoe plants grow on a wide range of host trees; they commonly reduce their growth and a large plant stunts and commonly kills the distal portion of branch it grows on. A heavy infestation may kill the entire host plant. Viscum album successfully parasitizes more than 200 tree and shrub species.

Technically, all mistletoe species are hemiparasites, because they do perform at least a little photosynthesis for at least a short period of their life cycle. However, this is academic in some species whose contribution is very nearly zero. For example, some species, such as Viscum minimum, that parasitize succulents, commonly species of Cactaceae or Euphorbiaceae, grow largely within the host plant, with hardly more than the flower and fruit emerging. Once they have germinated and attached to the circulatory system of the host, their photosynthesis reduces so far that it becomes insignificant.

While we can't be of much help with your Mistletoe we can help with whether you want desert landscaping, lush lawns or some type of landscaping in between, we can help.  We serve businesses like yours all over the Phoenix Metro Area. To find out how give us a call at 623-848-8277.

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