Being the festive season with mistletoe decorations and mistletoe kisses, this strange plant seemed a suitable subject for a blog, so here are some facts, superstitions and folklore...

As a plant without obvious roots or sources of food, it was once thought entirely magical and credited with extraordinary powers - giving rise to its use in medicine and a rich history of folklore. In the Middle Ages it was thought to break the death-like trances of epileptics, dispel tumours, divine treasure, keep witches at bay, and protect the crop of the trees on which it grew. Its use in the treatment of epilpsy continued into the 17th century and, as recently as 1993, a sixty-six year old man told of how, as a boy, he was given mistletoe by a gypsy woman to treat his epileptic fits, and that he had had no seizures since. I have seen mistletoe most commonly on Limes and Apples, but also on Hawthorn, Poplar, Willow, Rowan and False Acacia. It will undoubtedly grow on many other species but Pliny refers to its rarity on Oak, making 'Oak Mistletoe' highly valued for its 'powers' - Oliver Rackham questions if it is ever found on ancient Oak.

Enough myth and folklore - now for something completely different - a few mistletoe facts:

Mistletoe is in the Order Santales which includes the valuable and scented Sandalwood tree. The Order contains many epiphytes, parasites and hemi-parasites - including the Sandalwood tree itself which, when young at least, taps into the roots of a variety of host trees. Foresters growing Sandalwood in plantations will often use Acacia to start them off. Mistletoe is termed a hemi-parasite because its green leaves manufacture sugars by photosynthesis and it draws only water and mineral nutrients from the host.

There are over seventy species of Mistletoe worldwide, the European Mistletoe being the only one native to Britain. It prefers a mild, humid climate and good numbers of suitable host trees and is particularly common in a wide circle of land around the Severn estuary, where the valleys are moist and there is a tradition of fruit growing.

Whilst host trees can often tolerate some uninvited mistletoe, it can also be harmful, certainly killing branches and even whole trees if the 'infection' is heavy enough. Trees 'pull' water up through millions of tiny vessels, the pulling force being exerted by the osmotic pressure within the leaves and transpiration (evaporation) of water through leaf pores. The force is considerable and the millions of threads of water are as taught as piano wire. They can snap - something that is called cavitation but that a plumber might call an air lock, or a surgeon an embolus - and cells relying on the water from those vessels will die. Mistletoe can increase the tendency to cavitation and sometimes the water supply can give out and the host is killed by desiccation.

A sailor's wife had chestnuts in her lap,
And mounched and mounched and mounched.
'Give me,' quoth I.
'Aroint thee, witch!'
the rump-fed ronyon cries.

from Macbeth

Seasons Greetings! The obvious choice for December's Tree of the Month was the Christmas Tree, but for me roast chestnuts are such an essential part of Christmas festivities that this month it simply had to be the Sweet or Spanish Chestnut. I first tasted roast chestnuts many years ago at a Victorian Evening in my home town. It was a crisp cold December night and there was a small crowd gathering around the heat of the vendor's brazier, their breaths frozen clouds. Being curious, I handed over what was then a lot of money - a princely 50 pence - and in return I was handed an inconceivably small paper bag, little bigger than a matchbox, containing just three chestnuts. Feeling somewhat disgruntled, I headed down the street peeling one as I went. But then I popped it in my mouth... and I was in heaven. Now I knew what Nat King Cole was singing about! In 1662 Evelyn spoke of them as 'delicacies for princes and a lusty and masculine food for rusticks, and able to make women well-complexioned,' and then lamented that in England they are chiefly given to swine...but pigs industrially fed on them in Spain and Corsica also produce the caviar of the ham world - Jamon Iberico. I still regard roast chestnuts and chestnut stuffing as one of the highlights of Christmas and for that reason December's Tree of the Month 2016 must be the Sweet Chestnut:

Sweet Chestnut (Castanea sativa) is a member of the Fagaceae family - all have fruits in the form of a nut either enclosed within a spiny or scaly capsule or held like an egg in a cup. The commonest native trees of the family are Oak and Beech, but Sweet Chestnut has been here for some 2000 years and might be considered an honorary native. In fact it was long thought to be a native and the suggestion that it was not sparked some controversy at the Royal Society in 1769, the arguments that it was native being perfectly sound at the time. The earliest written record is in the Forest of Dean where Henry II granted the tithe of Chestnuts to Flaxley Abbey and in the New Forest there was a boscus castanearis in the 14th century. But a clue to the tree not being native is the relatively little folklore and superstition attached to it - showing that much folklore derives from pagan times. Even so, it was only with the advent of pollen analysis that it was finally shown to be an introduction.

Sweet Chestnut can grow to 100 ft or more and live to a great age, developing enormous trunks in the process - as in the above pictured impressive tree at Canford School in Dorset. Even larger is the famous Tortworth Chestnut in Gloucestershire, which I must visit, already described as a tree of legendary antiquity in 1706. Its subsiding branches have now taken root to develop 17 secondary trunks that form a 'wood' 30 yards across, complete with bluebells, dog's mercury, lesser celandine and garlic growing beneath. And even bigger still, which I really must visit if I can ever afford it, is the Hundred Horse Chestnut growing on Mt Etna which had a stem girth of 190 ft when measured in 1780. Confusingly, the Hundred Horse Chestnut is a Sweet Chestnut, not a Horse Chestnut, but is so called as it is said to have sheltered Queen Guivanna and her entourage of 100 knights when they were caught in a storm. The tree has now split into multiple stems and is fenced. A larger tree on Mt Etna died, reportedly succumbing to the repeated cutting of branches to fuel the fires to roast its chestnuts. That's killing the goose....and having no stuffing.

The leaves, which are relatively insect resistant,  are large, narrow and glossy, somewhat leathery in texture, 7 to 9 inches in length, about 2.5 inches wide, tapering to a point at each end. The deep mid-rib gives rise to side veins, each a valley ending in a saw-tooth point at the leaf margin, ideal for making 'fishbones' - the careful tearing out the soft leaf tissue to leave the skeleton. The leaves remain on the trees late in autumn, turning to a golden colour before a coppery brown. They are very efficient with less than 1% of light wavelengths useful for photosynthesis passing through, meaning little can grow well beneath a dense canopy. They are the only part of the tree listed by Maud Grieve's Modern Herbal (1931) as having a medicinal use - an infusion made from steeping dried leaves in boiling water being used to treat 'paroxysmal and convulsive coughs, such as whooping-cough, and other irritable and excitable conditions of the respiratory organs'.

Sweet Chestnut is sadly vulnerable to 'Chestnut Blight' a disease that decimated the American Chestnut (Castanea dentata). Caused by a fungus, Cryphonectria parasitica, the disease acts much like Dutch Elm disease, rapidly killing the tree but leaving the roots alive to resprout and grow, only for the disease to kill again when the tree reaches a certain size - and so on ad infinitum. The disease was imported to America between 1882 and 1904 on Asian Chestnuts and within 20 to 30 years it had killed 99.9% (about 3.5 billion) of the American Chestnuts in its native range of the Appalachian mountains, destroying it as a commercial crop. Squirrel populations crashed and seven species of moth living on the American Chestnut are now extinct. At about the same time it was first noted in Europe - but here there is some hope because in several parts of Europe some infected trees appear to have recovered. This has been associated with less virulent strains of the fungus that are thought to be infected with a virus that appears to have reduced the severity of the disease when used as a biological control. The disease was identified in 2007 in Warwickshire and again just this year in Kent. In both cases the trees had been imported from infected areas and planted here. The trees were destroyed and surrounding areas surveyed, but unfortunately they had been in the ground for four and seven years respectively before the disease was identified. Since 2013 imports of plants or seeds must have 'passports' to show they are not from an infected area and that timber has been fumigated or kiln dried. (Feb 2017 update: The Plant Health (Sweet Chestnut Blight) (England) Order 2017 ( http://www.legislation.gov.uk/uksi/2017/178/contents/made ) came into force February 2017. It controls the movement of Sweet Chestnut material within certain distances of 'demarcated areas'. There are currently two demarcated areas in Devon. Full details here: https://www.gov.uk/guidance/plant-health-controls#quarantine-pestsor http://www.forestry.gov.uk/chestnutblight ) 

sources:
Bean W. J Trees & Shrubs Hardy in the British Isles 8th Ed. Forestry.gov.uk - Chestnut Blight. Grieves M, A Modern Herbal, 1931. Johnson H, Trees 1973. Mabey R, Flora Britannica, 1996. More D & White J, Cassell's Trees, 2003. Rackham O. Ancient Woodland (2003 ed); Woodlands, 2006. Smith, D, Delia's Happy Christmas. Tudge, C. The Secret Life of Trees. Thomas P & Packham J, Ecology of Woodlands & Forests, 2007. Wikipedia. Wikimedia Commons