South-east Yorkshire, Articles


Longer articles

This page will be used for articles concerning East Yorkshire botany that are of a more substantial nature than those items posted on our News page. We would welcome any such items, particularly those which will provoke further discussion or research into our local flora.


THE BEECH ENIGMA - a discussion of views and personal observations regarding Fagus sylvatica in East Yorkshire.

J. Killingbeck, February 2017

There has long been a level of controversy regarding the status of beech as a British native tree. These controversies begin with the possibilities of whether the beech actually arrived in Britain entirely by natural means or was introduced intentionally by prehistoric man as a food source - beech nuts (Huntley 1997). This hypothesis argues that in all probability, by the time beech had advanced by natural progress as far as Northern France in the post glacial - the English Channel was already formed. If correct, other than man, its arrival here would depend on less probable natural agents such as Jays carrying nuts across the channel or even less plausibly, large mammals like bears swimming across with seeds in their digestive tract.

Native status was once further undermined by the oft quoted comment of Julius Caesar - "timber of every kind which is found in Gaul also grows in Britain, except Beech and Silver Fir". He was right about the fir, but how likely is it that a Roman general would be a reliable expert in all tree identification? Other scholars point out that he was referring strictly to 'timber' (usable wood) as opposed to the presence of the tree itself. Clear pre iron- age records of the tree also exist (Rackham 1997).

In spite of the above, the beech is generally accepted by most authorities as a British native tree, if one of the latest arrivals - though generally only so to the South East - roughly Suffolk to S.E. Wales. Like much knowledge of pre historic plant distribution, a lot of this is based on pollen analysis. But traces of ancient beech have been found well beyond this range, in one case as far north as Durham (Rackham 1997), which together with the fact that for beech, the ill drained ground which best favours pollen preservation is anathema, make some authorities think the traditional view of south eastern distribution too conservative or at least, may represent a contraction of range.

The case for native status in East Yorkshire is much more tenuous, yet has been seriously aired. Eva Crackles (1990) in her 'Flora' discusses this in connection with rare plant records normally associated with beech woods: (Cephalanthera damasonium; Epipactis phyllanthes also Monotropa hypopitys) all found otherwise improbably in the southern Wolds. This evidence is supported by J F Robinson in his 1902 flora, based also on the claim that the Roman name for Brough (Petuaria) means 'Beech Groves'. Yet given that Romano British references state that the name actually means 'a quarter or fourth', one wonders how Robinson came by this idea. Equally though, prehistoric evidence of beech has been found in north Lincolnshire - just across the river (Rackham 1997).

What of the tree itself? Beech has been planted so widely in the British Isles as to totally blur its natural distribution. And having been introduced it has proved able to produce viable seed and self- sown progeny as far north as the Scottish highlands. This fact makes the behaviour of beech in East Yorkshire all the more puzzling. Despite being so widely planted in the county as to seem native, particularly in the Wolds, it remains the exception rather than the rule to find evidence of significant self- regeneration. This 'enigma' is thus the subject of this article.

Many beech plantations and woods in East Yorkshire are not only entirely devoid of regenerated saplings, but their seed production, when examined often proves to consist of only barren husks lacking embryos. Beech certainly has a reputation for erratic seed production (mast years). This is generally associated with warm seasons and may explain the tree's association with the south. Yet for many, perhaps most beeches in East Yorks., no season seems good enough to induce a viable crop. Is the climate then too unfavourable even compared to the highlands? If so, in what respect? The most negative climatic influence may be the chill of the North Sea, notably at flowering time. However, of those woods that do regenerate, some are found in the higher parts of the Wolds whilst other trees at much warmer elevations fail to do so. Conversely, an (admittedly subjective) impression is gained that regeneration may have increased since the 1990s - perhaps as a response to slight climatic warming.

Another interesting feature of the regeneration pattern is that it is often particular individual trees in any wood that produce all the saplings. This is clearly evidenced by sapling distribution which may be quite dense under one or two trees, whilst almost absent under any others. What might account for this? Genetic variation is one obvious explanation related perhaps to provenance. Since beech is almost exclusively a planted tree in E. Yorks. the particular seed source may be significant if, say, imported from an area of continental Europe with consistently warm summers. Uniform seed sources of particular origin may explain why certain entire woods here seem unable to produce viable seed, whilst other woods seem better adapted to local conditions.

Yet many beeches in our area do often produce a prodigious crop of plump nuts, which, if they overhang a road can be seen squashed in their hundreds by passing traffic. But not all these trees are successful in producing even a single sapling. The seedlings of trees in field hedgerows and mown verges clearly stand little chance of survival and unlike many other trees, they seem less able to regenerate in hedges themselves. Yet others fail to reproduce in what would seem to be favourable conditions, even woods nurturing a crop of Ash and Sycamore. Is this due to particular soil conditions, mycorrhiza, acidity, moisture, competition? Equally though, some saplings occur under isolated trees in rough grass and exposure which would seem harsher.

This puzzle seems linked with instances of abundant seedlings which disappear at some point after germination. Presumably many of these are eaten by rodents, including squirrels. Established saplings can also be destroyed by rabbits and deer. Hares can remove the basal bark of quite mature trees. Such damage may be related to local animal population fluctuations, coinciding with harsh winters and a shortage of alternative food sources but need only occur less than once a decade to have a severe impact on beech regeneration. Any of this speculation may or may not be true but still begs the question why it would impact East Yorkshire trees more than is clearly the case elsewhere. The most likely guess would be the inter relationship between locally characteristic intensive agriculture - boom and bust food sources with little natural alternative - combined with severe predator control linked to intensive 'game' production, leading to unstable overpopulation of certain seed/bark eating animals, exacerbated by particular weather conditions. But this is only a guess.

Most East Yorkshire beech woods thus show at best a patchy ability to sustain themselves without the aid of man. However to add to the 'enigma', there are a few exceptions. Three examples come to mind: one above Nunburnholme, one above Londesborough and "Little Wold Plantation" above South Cave. The first two are characterised by stands of mature and over mature beech trees mixed with semi shaded clearings probably the result of natural tree fall. In both these woods abundant, even dense stands of beech saplings occur, the oldest of which are several metres high and showing every sign of growing to maturity. It seems this pattern of regeneration may be most favourable to beech. This hypothesis was reinforced about 20 years ago in another wood above Warter when a violent gale resulted in the fall of many mature beech. The following season hundreds of beech seedlings appeared. These developed into small saplings, before the remains of the wood were cleared and uniformly re planted with several species, including, ironically, beech.

Little Wold Plantation however is a study in itself. It consists of mostly semi mature beech canopy with predominantly ivy (Hedera helix) floor. Although the trees extant today were probably planted in the early c.20th, conceivably given its location, this wood may represent a relict fragment of the type 'native' beech wood (if such a thing existed) alluded to by Crackles and Robinson so is worth considering in this light. This is particularly in view not only of potential rare floral associates mentioned but because of currently prescribed management.

Rather like the Warter wood mentioned above, Little Wold Plantation suffered a 'gale event' in the early 1990s. And just like the Warter wood, the following season resulted in a mass germination of beech seedlings. These grew rapidly into dense vigorous stands within a few years - which then abruptly disappeared!

Though at first a seemingly incomprehensible event - this appears to have been attributable to management activity by the Woodland Trust, who acquired the wood later in the decade. A perusal of the management plan indicates a policy of beech (and other 'inappropriate' tree) replacement by ash (Fraxinus excelsior) in order to achieve a pure ash wood ecology in the future. This policy is based on the generalised view that beech is an alien invasive species in northern England and that ash wood represents the 'natural' climax forest in such regions as the Wolds - even though human activity does seem closely linked with ash abundance in the pollen record (thus probably mainly semi natural). Although beech has continued to regenerate at Little Wold along with some ash and sycamore (Acer pseudoplatanus), the policy of discouraging beech continues, though presumably, short of significant felling of the existing trees, it may be a century or so at least before ash replaces beech as a mature dominant. The more sophisticated elements of ash wood ecology may take considerably longer. The wisdom of this strategy is questioned even in the management plan itself, because of the threat posed by ash dieback disease (Chalara fraxinea), the impact of which is only starting to become apparent.

With the above in mind perhaps it is worth reconsidering several points. In what sense will an attempt to recreate ash wood here represent a natural vegetation? In the context of what has been termed 'The Anthropocene', does the idea of what is 'natural' have any real meaning, or does the aim to create ash woodland here today represent much more than the latest imposition of human will on what is deemed 'nature'? Is it more truthfully an arbitrary, perhaps imaginary historical ideal in the development of vegetation since the last ice age - made essentially 'unreal' by the wider influences of the Anthropocene (atmospheric and soil pollution, climate change, introduced pathogens, massive disturbance and so on)? Would ash wood policy be more justified had Little Wold already been predominantly ash rather than as it seems, a reversal of the current status and if the Crackles/Robinson hypothesis is correct - a reversal of historical ecological significance? "Conservation … is a human activity ruled by fashion" (Rackham 1997).

It has been suggested that under the influence of climate change, not only should native trees like beech be allowed to migrate northward, but even that their very survival might depend on it. It seems likely that left to their own devices, they would have done so, just as they did in the prehistoric past (Peterken 1997). Little Wold and other examples mentioned might represent a vanguard of this movement. How much more might be learned about the behaviour, ecology and adaptability of our native trees facing this uncertain future by allowing and studying their own attempt to change and adapt, rather than constraining them in a model that may have been applicable long ago, but now could be deemed pastiche? And in the intensively managed, thinly wooded landscape of East Yorkshire - how very rarely such opportunities arise.

References and bibliography:

Crackles E (1990) - Flora of the East Riding of Yorkshire - Hull Uni. Press

Flenley JR (1990) - Vegetational History ch4, Humber Perspectives (Ellis & Crowther) Hull Uni. Press

Huntley B (1998) - The Post Glacial History of British Woodlands ch.1, Woodland in the Landscape: Past and Future Perspectives (Atherden & Butlin) -Leeds Uni. Press

Kirby K (1992) - Ancient Woodland: A Re-creatable Resource? - Tree News (journal) - Severnprint

Pennington W (1969) - The History of British Vegetation - English Universities Press

Peterken G (1997) - Natural Forestry - Tree News (Journal) - Severnprint

Rackham O. (2014) - The Ash Tree - Little Toller Books

Rackham O (1998) - Woodland Conservation: Past, Present and Future ch4, Woodland in The Landscape (as above, Atherden & Butlin) Leeds Uni. Press

Rackham O (1997) - Where is Beech Native? - Tree News (journal) - Severnprint

Tansley A G (1965) - The British Islands and their Vegetation - vol. 1 - Cambridge Uni. Press

Some Useful Websites Referred To:

'Petuaria' - Wikipedia and other related sites

Woodland Trust - East Yorkshire - Little Wold Plantation - Management Plan

Asian Bittercress (Cardamine occulta) - has it arrived unnoticed?

Peter J Cook, 26 April 2016

In the last 12 months we have become aware of the occurrence of New Zealand Bittercress Cardamine corymbosa which, together with both Hairy Bittercress C. hirsuta and Wavy Bittercress C. flexuosa, now make up a trio of weedy bittercresses to try our identification skills.

A paper published by Marhold et al. in PhytoKeys introduces the possibility of a fourth species, Asian Bittercress C. occulta, which is spreading across Europe from the paddy fields of Italy, where it was introduced in Asian rice seed. Its first appearance outside Italy was in Spain in 1993 and subsequently there have been numerous records across Europe including, by 2009, The Netherlands from where many of our bedding plants are imported. It grows in flower beds and pots, at the edges of roads, among cobblestones or paving stones, or on pavements, often in irrigated places. In most cases, it has apparently been introduced as a weed, often with mulch, from plant nurseries where it finds appropriate growing conditions. Morphologically it differs little from C. flexuosa.

Cardamine flexuosa?

We have recorded an apparent increase of C. flexuosa in man-made habitats since we started recording for Atlas 2020. The current tetrad maps for C. flexuosa shows concentration in e.g. Bridlington, Hornsea, Withernsea and Hull. I have been ready to believe that it has been introduced into gardens with bark chips of forestry origin, used as mulch. Indeed, Marhold mentions this as a possible means of spread of C. flexuosa into urban gardens. However, it could be C. occulta being spread the same way.

Pictured left is a 40 cm specimen of bittercress gathered today from a sheltered, very wet garden in Withernsea. The garden has a history of being planted out with annual bedding plants obtained from local nurseries. The specimen fits the description of C. flexuosa with its sinuate, deeply grooved stems up to 3 mm diameter, hairy leaves and in each of the 6 flowers I examined, 6 stamens. Formed fruit do not exceed the inflorescence. I think this could be C. occulta.

As far as I can tell there are no UK records for C. occulta and I think it would be useful for us to press down a collection of specimens of C. flexuosa finds from wet or frequently watered urban gardens pending expert examination. The two species are segregated by chromosome counts; C. flexuosa is tetraploid whereas C. occulta is octoploid.

Reference: Karol Marhold, Marek Šlenker, Hiroshi Kudoh, Judita Zozomová-Lihová. Cardamine occulta, the correct species name for invasive Asian plants previously classified as C. flexuosa, and its occurrence in Europe. PhytoKeys 62: 57-72 (25 Mar 2016)

An Exploration of Mistletoe (Viscum album)

John Killingbeck, January 2016

This is a short article describing the distribution of mistletoe in the East Riding of Yorkshire (v.c.61), based on chance personal encounter and including some speculative comments. Although described by Stace as native north to Yorkshire, those who know the plant will be aware that it has a somewhat anomalous distribution in the UK, being generally uncommon and rather localised in southern Britain except in the Severn valley counties where it appears abundantly and quite commonplace.

Interestingly, its distribution in East Yorkshire appears similarly anomalous. In general it is very scarce, even perhaps almost unknown west of the Wolds - and in many parts to the east, hardly encountered. Yet there are one or two enclaves where it is quite abundant and a scatter of other places mainly in the general arc of the river Hull between Hull and Driffield where it may be encountered. It is probable that some clumps of mistletoe have been deliberately cultured - not an easy task but not beyond the skill of some. Such clumps are likely to be found fairly low down on apple trees and to be isolated from other plants. Once established such a clump may increase on its host but seems rarely to go beyond it. However there are many other plants which are far too high above the ground to have been deliberate and these are the more interesting from a botanist's point of view.

The Hull area has a number of records. Most likely hosts include: apple, Malus domestica, Common lime, Tilia x europaea, (though in Western Cemetery it has also been seen on Tilia tomentosa) and hybrid black poplars, Populus x canadensis vars. Some old records are mentioned in Eva Crackles' Flora of East Yorkshire. The Hull enclave spreads into the western suburb of Hessle, where a large clump can be seen on a lime in Hessle square and formally on the more unusual host, American Black Walnut, Juglans nigra in the cemetery. This latter clump seems to have died out. Black walnut, incidentally, is a known host in other parts of the UK. The farthest flung limit of the Hull enclave so far is at Skidby, where a plant has recently appeared on a form of hybrid poplar.

A second substantial enclave of mistletoe is to be found in Beverley, centred on the Manor Road district. The epicentre of the colony seems to be an old orchard behind Manor Close, now almost obscured by housing. Old apples here are laden with large mistletoes. From here the colony has spread, most conspicuously and quite prolifically to the tall limes behind Beverley High School. A nearby poplar, in the opposite direction, was also infested by several clumps until recently felled for no obvious reason. In nearby gardens, rowan, Sorbus aucuparia is also infected. An outlying clump grows on a lime at the old County Hall building.

A third strong and very diverse enclave is to be found in the village of Lockington, to the north - but scarcely beyond it. Here, clumps may be encountered on lime, apple and poplar, but also on willow, Salix fragilis, hawthorn, Crataegus monogyna and even robinia, Robinia pseudoacacia (an unlikely but common host in the south). There are probably well in excess of 20 clumps spread round the village.

A little to the north is the small settlement of Cawkeld. Here is another small cluster of mistletoes most of which are confined to large hybrid poplars, though with one also on hawthorn. And close by to the west, one apple in South Dalton bore mistletoe, though has since died. This last may be deliberate, being very low, and despite being surrounded by suitable hosts, has failed to spread.

The final mistletoe enclave in the county centres around Driffield. A group of plants infests willow close to the western bypass of the town and another on hybrid poplar to the south. Until a few years ago an ornamental Malus in a suburban street bore a clump but was unluckily chosen to be felled in a simple thinning out exercise by the local council. The fate of this and the Beverley poplar underlines the constant threat to mistletoe in the county - that of inadvertent destruction. It is unfortunate that mistletoe seems generally to favour large, old and or decrepit trees, those most likely to be removed.

The above summarises my knowledge of the main mistletoe enclaves in the county, though no doubt there may be others. A main point of intrigue is why in these particular enclaves the plant seems to have spread, whilst in other places it remains clinging to a single original host (probably introduced) and goes no further and why generally it does not seem more evenly spread over the county?

Website managed by Richard Middleton: last updated on 12 February 2017