20. Mistletoe

 Viscum album.

This is a lime tree just down the road from my house, with several outbreaks of mistletoe on it, the largest clump on the left was about 1 m across. Just down the road from this spot was a poplar with a clump as big as a garden shed, over 2 m across.

Mistletoe is an obligate stem hemiparasite, it needs to live on a tree to survive (obligated to), but doesn't entirely get all its energy from the tree as it can photosynthesise too (semi or hemi-parasitic). 

Mistletoe - or as it was called in Old English Mistletan - has a great etymology, 'Mistle' means shit and 'tan' means twig, hence mistletoe =  shit twig. Which I rather like because this very old word describes part of mistletoes life cycle. 

Our ancestors noticed that mistletoe appears under bird roosts, for good reason, let me explain... 

The Mistle Thrush has a Latin name with another pooh reference Turdus viscivorus, 

Mistle thrushes eat mistletoe berries in winter when they fruit, the berries are obviously tasty, but also a laxative, the thrush eats the berries whole (unlike the black cap which I will deal with later) including the seed, 30 minutes later or less, the thrush excretes the berry seed in a sticky gloop. 

Hence if the Turdus viscivorus has a regular spot to drop a turd, beneath that favourite toilet branch will be a collection of turds on branches, or shit on twigs, or old English... 'mistletan'.

From the thrushes droppings some mistletoe seeds germinate and grow into any flaw in the tree bark and thus invade the xylem tissue to extract nutrients.

  Mistle Thrush Turdus viscivorus beside mistletoe.

  The black cap Sylvia atricapilla is probably better at spreading mistletoe seeds than

the thrush, the black cap doesnt like to eat the seeds, so having eaten a few berries it then wipes its beak on the branches to get the sticky seeds off. thereby pushing the seeds into any flaws in the bark.

Hence not only is Mistletoe obligated to a host tree it is also obligated to these two birds to propagate its seeds

RSPB website (2020) Mistle Thrush. Available at: https://www.rspb.org.uk/ (Accessed on: 17/03/2020)

RSPB website (2020) Black cap. Available at: https://www.rspb.org.uk/ (Accessed on: 17/03/2020)

The Wildlife Trusts (2020) Where to see mistletoe. Available at: https://www.wildlifetrusts.org/where_to_see_mistletoe  (Accessed on: 23/03/2020)