Thursday, 29 January 2009

An Urban Parasite

A plant parasite is a plant which grows on another plant and steals nutrients from it. Mistletoe (Viscum album) is a parasite which grows on a wide variety of trees both native and non-native. Strictly speaking, Mistletoe is a ‘hemi-parasite’, that is, it steals minerals and water from its host but it is also semi-evergreen and so manufactures some of its own food, through the process of photosynthesis, like other plants (1).
Mistletoe plants are either male or female. The tiny, yellow-green flowers open in March and are wind-pollinated. They have either four minute anthers or a hidden ovary. The latter develops, after fertilisation, into a white berry. These berries are palatable to mistle thrushes and other birds. The seeds are sticky and tend to stick to the beaks of the birds that eat them. In attempting to dislodge the seeds the birds often rub them off on to tree bark and into crevices. The germinating seed produces roots which invade the tree for nourishment and develops into a green shoot which divides repeatedly until the plant becomes a ‘bush’ which can be 2.0m across (2).
Oliver Rackham (3) states that, “Mistletoe ... is usually seen on exotic trees – cultivated apple, hybrid lime and hybrid poplar – with a preference for old specimens” and that, “it has a natural habitat on ancient native trees, especially hawthorns”. He also tells us that, “it very rarely occurs in woods, ancient or recent” and that, “It is very rare on oak”. In another passage he states that it is, “A specifically savanna plant” and that the presence of its pollen in the pollen record tends to indicate a warm period in which the savanna habitat (open grassland with scattered trees) was dominant. He goes on to describe Hatfield Forest, in Essex, which, “is its (i.e. Mistletoe’s) chief stronghold on wild trees, it occurs on old hawthorns and old maples, but only in the plains, and not in the woods.”
I have seen Mistletoe growing on an old, isolated hawthorn on Barnack Hills and Holes National Nature Reserve in Cambridgeshire – little did I realise, at the time that I was being afforded a glimpse of an ancient savanna!
In Britain Mistletoe is found in England and Wales, northwards to Yorkshire. It is mostly local in its occurrences but it is especially common in those southern parts of the English/Welsh borders either side of the Severn Estuary (4). I have seen apple orchards in Herefordshire where every other tree seemed to bear a heavy burden of Mistletoe.
Just before Christmas 2008 I was on the top-deck of the number 23 bus, returning to Chorlton from Stockport. All around me noise was blasting out from digital ‘post-music noise’ generators which were competing with the loud, one-sided conversations that people were holding on their mobile phones. On the outskirts of Didsbury village I involuntarily added to the cacophony by emitting a small squeak of surprise (I think I got away with it!). The cause of my minor outburst was a glimpse of the distinctive ‘starburst’ shape of a Mistletoe plant in a lime tree. Until that moment I had assumed that we had no Mistletoe in South Manchester. When, a few days later, I mentioned this sighting to Alison Hunt, of West Didsbury Residents’ Association, she said that she had also seen it in West Didsbury and directed me to another two lime trees hosting Mistletoe plants (5). Subsequently I learned, from members of Manchester Field Club, that there used to be a Mistletoe plant on an old apple tree in Fletcher Moss Gardens (6). The tree was cut down a few years ago – but perhaps it was the original source of the lime tree infestations observed by Alison and me?
In his great cultural flora, ‘Flora Britannica’, Richard Mabey (7) tells us that Mistletoe was, “one of the most revered plants of early herbalists” and it was credited with extraordinary powers, both curative and magical. It was also, and occasionally still is, the focus of much folklore and many customs – particularly in those regions where it is common. Some of this lore may be very old but Mabey urges caution over linking Mistletoe with ancient druidic practices. Briefly, the druids were supposed to have used golden sickles to harvest Mistletoe from oak trees and to have used it in their sacred rituals. It appears that much of this story was invented in the 18th century by an eccentric, antiquarian cleric, called William Stukeley, who read far too much into some vague hints in a book by the Roman author, Pliny.
Mistletoe has also been associated with fertility and this is probably why people still kiss under it at Christmas time. I’ll leave you with a verse from a favourite poem entitled ‘Christmass’ from John Clare’s, ‘The Shepherd’s Calendar’ (published 1827) (8):

The shepherd now no more afraid
Since custom doth the chance bestow
Starts up to kiss the giggling maid
Beneath the branch of mizzletoe
That neath each cottage beam is seen
Wi pearl-like-berrys shining gay
The shadow still of what hath been
Which fashion yearly fades away

Dave Bishop, January 2009


1. Wikipedia article on Mistletoe and Relatives: http://en.wikipedia.org/wiki/Mistletoe

2. ‘Book of the British Countryside’, Drive Publications, 1973

3. ‘Woodlands’ by Oliver Rackham, Collins, 2006

4. ‘Interactive Flora of the British Isles’ (DVD ROM) by C.A. Stace, eds R. van der Meijden & I. de Kort, ETI bioinformatics, 2004

5. Personal Communication from A. Hunt (West Didsbury Residents’ Association), December 2008

6. Personal Communication from A. Locksley, P. Tolfree and A. Hill (Manchester Field Club), January 2009

7. ‘Flora Britannica’ by Richard Mabey, Sinclair-Stevenson, 1996

8. ‘The Shepherd’s Calendar’ by John Clare, eds. Eric Robinson & Geoffrey Summerfield, Oxford, 196?

Monday, 26 January 2009

An Urban Epiphyte

An epiphyte is a plant which grows on another plant without parasitising it(1). In the best known examples the host plant is usually a tree. Epiphytes are particularly common in tropical rain forests and many different types of plants can be involved, for example, ferns, orchids, bromeliads and even cacti. An epiphyte has some advantages over plants growing on the ground, for example less competition and increased light levels. On the other hand such a plant is likely to experience lower levels of nutrients and water.
Because of the danger of drought and drying out, epiphytes tend to be found in areas with high rainfall. In Britain and Ireland most epiphytes are found among the so-called ‘lower plants’ (i.e. mosses and liverworts) but some ‘vascular’ plants (i.e. plants with stems) are involved, particularly ferns and particularly ferns in the genus Polypodium (often referred to as ‘polypodies’). As a result of the higher rainfall requirements you are more likely to see epiphytic polypodies (and other epiphytes) in Ireland and the western side of the island of Britain than you are on the drier eastern side(2). Nevertheless, epiphytic polypodies are usually confined to old woods in remote rural locations such as parts of Ireland, Wales, western Scotland and western England. A famous location is Wistman’s Wood on Dartmoor. This is an ancient oak wood in which, “... [the oaks’] crooked branches [are] festooned with mosses and lichens, with ferns and even young trees sprouting from their clefts”(3). Although polypody ferns are reasonably common on old walls in South Manchester (for example the walls of Withington Sewage Works near Hardy Farm), until recently the only vaguely epiphytic one that I had seen was growing on a, decidedly dead, elder bough in one of the compounds on Chorlton Ees.
Then last year (2008) I received an email from local conservationist, Leon Patsalides (the founder of the Friends of Hough End) telling me of a fern that he had spotted growing on a street tree on Upper Chorlton Road; he called it a “sky-walking fern”(4). Next time that I travelled along that road, on the top deck of the number 86 bus, I kept my eyes open for it, and eventually spotted three examples. All three were Polypodium species growing on London Plane trees at between about 3.5 to 7.0m above street level and usually in the crotch of the tree at the point at which the main trunk begins to branch. The photograph above shows, what is probably, the best example on the corner of Wood Road and Upper Chorlton Road.
I mentioned this discovery to Audrey Locksley of the Manchester Field Club and she said that she had seen the same phenomenon on Urmston Lane(5). Subsequently, I walked the length of Urmston Lane, from the centre of Urmston to Stretford, and spotted seven more examples. Nevertheless, the phenomenon doesn’t appear to be particularly common and I have now examined dozens of plane trees, on main roads, side streets and parks and have not spotted any more.

A note on the species involved is in order here:

The ferns are just out of reach (and I tend not to carry a ladder around with me!) – so I have not been able to obtain a specimen for identification. My educated guess is that they are most likely to be Intermediate Polypody (Polypodium interjectum) as this is the species present on the walls of Withington Sewage Works(6) and they look very similar. The tree is invariably London Plane (Platanus x hispanica) which is a man-made hybrid between the Oriental Plane (P. orientalis) and the American Plane (P. occidentalis)(7). London Plane was first grown in Britain at the end of the 17th century and became a preferred street tree, first in London, then in other cities in the UK, because of its resistance to pollution and its general hardiness. In the wilder corners of Britain you are most likely to see epiphytic polypodies on oak trees (Quercus sp.)(2) but, in South Manchester, I have not seen a single fern on a single oak.
In conclusion, this may be a genuinely new urban phenomenon but it’s difficult to give any sort of explanation. And it’s particularly difficult to explain why only plane trees appear to be involved and why it only seems to occur on certain busy main roads.
If anyone spots any more epiphytic ferns, on any more local trees, I hope that they will let me know.

Dave Bishop, January 2009
1.For more information on epiphytes see: www.kew.org/ksheets/epiphytes.html

2. ‘Woodlands’ by Oliver Rackham, Collins 2006.

3. ‘The Wild Woods’ by Peter Marren, David & Charles, 1992.

4. Personal communication from Leon Patsalides, February 2008.

5. Personal communication from Audrey Locksley, March 2008.

6. Letter from Dr. F. Rumsey (Natural History Museum) to Ms. P. Tolfree re: ‘The Identification of Polypodium Ferns from the walls of Withington Sewage Works, near Brookburn Rd., Chorlton’, 2nd February, 2006.

7. ‘A Field Guide to the Trees of Britain and Northern Europe’ by Alan Mitchell, Collins 1974.

Saturday, 24 January 2009

A Greenfinch Variant

FoCM Treasurer, John Agar recently spotted an unusual bird on his garden bird feeder and wrote the following account of it:

Several weeks ago I noticed what appeared to be an all yellow bird among a mixed flock of Finches feeding on Niger seed sited in my garden. Unable to make an identification, I moved the feeder nearer to the house and was able to take the following pictures. The quality is not very good (photography not being my forte) but good enough to identify the bird as a Greenfinch. I hesitate to call it a mutant as apart from the colour it appeared to be identical to the other Greenfinches as can be observed from the photograph. I have to confess my memory seems to have let me down, there is a technical term to describe the variation of colour in species but for the life of me I cannot remember it*. If anyone can come to my rescue please do so.

Again if you disagree with my identification please let me know. I have both Goldfinch and Chaffinch visit the garden regularly along with several other species.

John Agar, January 2009

* I think that the term is 'leucism'. For more information see http://www.wildlifeextra.com/go/news/leucism.html - ed.

Friday, 23 January 2009

Completion of the Hardy Farm Project

We have now finished the project to improve the fruit woodland at Hardy Farm. We embarked on this project as a result of being awarded a Breathing Places Grant from the Big Lottery Fund in May 2007.In his letter to me thanking FoCM for the submission of the end of grant report, Jamie Thompson, Grants Officer for the Big Lottery Fund wrote:"I was pleased to see that your project has been very successful.The activities you have undertaken have made a great improvement to Hardy Farm, while providing many volunteers with accredited training. Well done for making such good use of your grant."So, thanks to the Big Lottery for giving us the chance to undertake this project and thanks to everyone who took part.

Dave Bishop, January 2009

Thursday, 15 January 2009

Song Thrush Anvil at Dry-Stone Wall.

Just thought I’d post an interesting observation at the dry-stone wall in Hardy Farm – see post dated 18/06/08

Originally designed to be a haven for invertebrates and small mammals, as well as – as pointed out by Dave – lichens and ferns – the dry-stone wall is also proving beneficial to birds. Walking by there a couple of days ago I noticed a few broken snail shells around the base – the tell-tale signs of a song thrush’s anvil: a stone used by the song thrush to smash snails against.

Reading here, it seems this is a tactic song thrushes tend to employ when the ground becomes either frozen or baked, making their usual food choice of worms difficult. This tallies nicely with the recent frosts we’ve had.

Anyone passing with a camera, please email in a photo!

Julian Robinson.

Wednesday, 14 January 2009

Book Review

Beechcombings by Richard Mabey, Vintage Books, Paperback ed. 2008 (ISBN 9781844139200), 289 pp, £8.99

If you have any interest at all in the British countryside and its wildlife then Richard Mabey’s books are essential reading. And if you’re interested in trees, and are confused by the plethora of books available on that subject, this present title is an excellent place to start.
Mabey’s books are always full of interesting information and thought-provoking concepts – and this recent title is no exception. Another characteristic of all his books is their personal quality – he never hesitates to tell us what he feels about the subjects that he observes and researches so thoroughly. If I may be allowed a personal note of my own, it is that Mabey has probably influenced the way that I see the world more than any other writer (and I have been reading him for more than half my life now). He has also directed me towards several other interesting writers. For example he alerted me to the importance of the 19th century labourer poet, John Clare whose native village of Helpston is within 10 miles of where I grew up in Peterborough (fittingly, Mabey is now the Patron of the John Clare Society). He also introduced me to the writings of that remarkable student of the British landscape, Oliver Rackham.
Mabey grew up in Berkhamsted in the Chilterns (you can see the remains of Berkhamsted’s Norman keep from the Manchester to Euston train). Beeches and beech woods are a feature of the Chilterns and hence Mabey has chosen to make the beech the focus of this book because, he tells us, “it has been the key tree in my own life.” Beeches are only native to certain parts of Southern Britain; we do have some fine examples in the Mersey Valley (e.g. at Jackson’s Boat and Ford Lane in Didsbury) but these were probably planted in the last 100 years or so.
Through a series of “discursive essays” , with the ‘beech focus’ described above, Mabey tells us of the history of trees in post-Ice Age Britain, the mythical ‘timber crisis’ during the naval wars of the 17th and 18th centuries and the subsequent invention of the plantation, tree-planting on great estates and its contribution to the social status of the estates' owners, the various explorations of natural beauty undertaken during the 18th century Enlightenment, the endless struggles between the forces of ‘development’ and ‘conservation’ which raged through the 19th and 20th centuries and continue on into the 21st century and the modern ecological view of trees and their role(s).
In a particularly interesting and illuminating passage Mabey identifies the ‘Great Storm’ of October 1987, which swept through southern England and laid flat 15 million trees, as a defining moment in our relationship with trees. Apparently ‘healthy’ (often planted) trees blew down whilst old, contorted ‘diseased’ veterans remained unscathed; and the subsequent ‘tidying-up’ of the aftermath of this remarkable event often did more damage than the storm itself. In subsequent years Nature showed remarkable powers of recovery and many wooded landscapes were given a new lease of life as a result of being thinned out.
For me the most depressing aspect of this text is the confirmation of my suspicions that many people remain remarkably ignorant about trees and continue to misunderstand and mythologise them. After the 1987 event the Tree Council (no less!) released the following press statement: “Trees are at great danger from nature.” Mabey describes this as an “extraordinary solecism” - which is a very polite way of putting it! He also tells us that when he shows someone an ancient tree or wood the question that he is most often asked is, “when was it planted ?” - as if, “The idea that trees have successful reproductive systems of their own seems to have passed out of the popular imagination.”
We live at a time in which the biodiversity of our country and of the world is under threat as never before. This threat cannot possibly be reduced if we do not understand the things that we are supposed to be protecting. This fine book should give everyone who reads it a better understanding of trees and our relationship to them.

Dave Bishop, January 2009

Wednesday, 7 January 2009

On New Year’s Day John Agar and I went for a walk in the Mersey Valley. More accurately we trailed along behind a larger, more organised group of ‘dedicated’ walkers. Because we dawdled along and stopped frequently to look at things and to take photographs we soon got left behind. Personally, I’ve never been keen on striding about for the sake of it – but I had an excuse on that day because I was still recovering from a nasty chest infection which had afflicted me over the Christmas period.
Nevertheless, I think we saw some interesting things which the others probably missed.
On Ivy Green the frost had wrought its usual magic and, transformed the dead stems of Ragwort, Hogweed, Thistles, Willowherb and various grasses with a gleaming white coating of ice crystals. In one of the fenced-off compounds on Chorlton Ees the magnificent ‘shuttlecocks’ of Scaly Male Fern were still standing (albeit a bit battered) and still green beneath their coating of frost.
We walked along the river bank to the Metro Line at Stretford then crossed the river to Sale Water Park. There was a fair amount of bird life on the lake and I took some pictures of some Cormorants on one of the jetties. These fish-eating sea birds have been moving inland and feeding at sites like Sale Water Park for some decades now; I remember first seeing them at Sale at least 25 years ago. Further along we saw some strange looking ducks among flocks of Canada Geese, Black-headed Gulls and Mallards all being fed by delighted small children and their parents. John identified the strange birds as Muscovy Ducks. According to the name these birds should be from Russia (‘Muscovy’ = ‘of Moscow’) but, in fact, they are from Central and South America and no-one appears to be quite sure where the ‘Muscovy’ name comes from (moral: never trust common names for things!). These ducks had either pure white plumage or white plumage with black wings bars and black flecks on the head. They also had bright red, wrinkly skin around their eyes and claws on their webbed feet. John told me that they have been present at Sale for some years but was not sure where they had come from. According to an article on the Internet they are now naturalised in several parts of North America and Europe.
We continued along the outflow channel which links the Water Park with the river near Jackson’s Boat. This is a favourite spot in spring and summer because it is very rich in water plants. In the channel some small ducks caught my eye and John identified them as Teal - which are Europe’s smallest duck. The females (‘ducks’) are pale brown with darker brown flecks but the males (‘drakes’) are more brightly coloured with chestnut heads with a bordered green stripe over the eye.
These little ducks are very fast flyers and, I suspect, could normally be quite difficult to photograph but, under the bone-chilling conditions of New Year’s Day, they fell easy prey to my camera.
We caught up with the rest of the party at Jackson’s Boat where they were planning to carry on along the river to Chorlton Water Park. Unfortunately, by this time, my chest infection was beginning to take its toll and I was flagging a bit so John and I sloped off back to my place for a cup of tea.
My photographs can be found in the ‘Birds’ album attached to this blog – see:
or just double click on the little slideshow on the right-hand side of this page.
Dave Bishop, January 2009.