What is it?

What is mistletoe?

Large growths of Mistletoe, Viscum album, on a Poplar tree. Poplars are a particularly susceptible host in Britain and northern Europe.

The familiar white-berried Christmas mistletoe of Europe is just one of many hundreds of mistletoe species worldwide. All are plant parasites, growing on tree branches (though a few grow on roots), and in their native lands many have similar folklore and superstitions to our own species.

Strictly speaking most mistletoes are only ‘hemi-parasitic’ as most have green leaves to photosynthesize and rely on their host for ‘just’ water and mineral nutrients.  But the interaction is often more complex than this, with some exchange of metabolites between host and parasite vascular systems too.

Many have peculiar pollination systems, and most have interesting insect and bird associations too.  You’ll find more information on all these aspects by browsing through the menu tabs above.

As parasites they do, of course, seriously distort and suppress the host branch they grow on.  That’s not a problem if just one or two branches are affected – but if the mistletoe becomes established on every branch it’s bad news for the tree and, ultimately, the mistletoe.

This diagram, from Julius Sachs’ 1887 Lectures on Plant Physiology, shows a mistletoe ‘haustorium’ – the distortion of the host caused by the infection. This is fairly simple example but the central swelling and reduction (to the right) of the host branch is easily seen.

A tree with too much mistletoe will suffer from insufficient of its own foliage, become water- and wind stressed because of the mistletoe growths and may well die prematurely.  The problem can be easily reduced through active management, pruning the mistletoe back from time to time, but sometimes it does get out of hand.  For information on a long-term survey project researching mistletoe management in Britain visit our Mistletoe Survey page.

Mistletoes pose intriguing biological and evolutionary questions for the biologist, and sometimes problems for tree managers and foresters, but to most people they are only interesting for their traditions and folklore – especially the Christmas kissing tradition.  Visit the Tradition pages for more about that!

For more about our ‘original’ European mistletoe visit our ‘Original’ Mistletoe page, and do visit our Other Mistletoes and Other Parasitic Plants pages too.

 

This page is part of the What is Mistletoe menu tab.  Other pages in this tab include The Original Mistletoe, Other Mistletoes, and Other Parasitic Plants.