The scientific name for the European mistletoe species which gave origin to the myth and tradition is Viscum album and it belongs to the botanical family Viscaceae. Its distribution is restricted to Europe where it is widespread. How widespread? Take a look on this map. However, the term mistletoe makes reference to a wider assemblage of plants which are all parasites on branches of host trees with a couple of species being root parasites. All mistletoes are included on the order Santalales, but distributed in different families within this order. Viscaceae is one of the major families and another one is Loranthaceae, known as the “showy-mistletoes” due to the big, bright-colored flowers of most of its species as for example, Psittacanthus dichrous, which is very common in Brazil.

There are over 4000 species of parasitic plants all together and they can be split into either hemiparasites, such as the mistletoes, or holoparasites, such as the dodder (Cuscuta sp) and Rafflesia arnoldii, which is the biggest flower in the world. “Hemi” means half, and “holo” means complete. Both types of parasitic plants make use of the haustoria, but the hemiparasites have chlorophyll and thus are still able to process photosynthesis. They tap into the xylem of host plants and deviate part of its water and raw nutrients. The holoparasites on the other hand, have lost all chorophyll and, not being able to make photosynthesis anymore, tap into the phloem of the host plants, stealing part of the host’s food. Click here to learn more about xylem and phloem. Watch this video and you can learn more about the fascinating Dodder and how the haustoria work at the cells level.

Many parasitic plants are considered pests, but that is only because they overgrow on crop areas. The dwarf mistletoe growing on timber crop areas is a good example and so are plants of the genus Striga. However, on natural environments, parasitic plants, as well as other plants, tend to an equilibrium where none will overtake the others. Moreover, some mistletoes, specially Viscum album, have been extensively researched on its medicinal properties, including its utility on the treatment of cancer. We can then conclude that being classified as “good” or as “bad”, depends on human intervention, perception and use of something.

The ultimate website where you can learn more about all parasitic plants, including many good images, scientific papers and other links is the Parasitic Plant Connection, built and kept by Dr Daniel Nickrent, one of the world’s leading specialists in these very peculiar and interesting plants. Visit it to learn more!

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