Worcestershire Record No. 3 November 1997 p. 4


Will Watson, Wildlife Consultant

English Elm Ulmus procera Salisbury (syn. Ulmus campestris Miller)

There are three species of elm and several interspecific hybrid combinations that are either native or naturalised in Worcestershire. English Elm Ulmus procera is by far the most widespread of the three species. In spite of the ravages of Dutch Elm Disease it is probably found within most 1x1 km squares in the county. Its characteristics are that mature trees have a massive straight trunk persisting half way through the crown, the bark is deeply cracked which in maturity form square plates, there are branches at all levels which twist and ascend at the top of a dense domed crown, lower limbs become rapidly diffuse becoming short and slender. In sub-mature trees the majority of branches are ascending. The leaves are 5-9cm in length, ovate to circular with a short pointed apex; they are harshly roughened above and rough on the underside, when fully developed they are unusually curled or puckered (Mitchell 1994). The leaves are nearly always attacked by the elm leaf-gall mite Eriophytes ulmicola (Rackham 1980).

The reasons for English Elm's U. procera continued widespread distribution is that it is native to our region and was widely planted right throughout the medieval period through to the 20th century, mainly in hedgerows (Rackham 1994). Although all mature English Elm trees have succumbed to the disease it survives in hedgerows because of its ability to produce vegetative suckers. Indeed it has largely abandoned sex as a means of reproduction. Its success is further enhanced by the fact that it is invasive and over time out-competes neighbouring species - hence where English Elm U. procera is present we get dominant stretches of elm hedges and dominant stands of suckering elm in woodland (Peterken 1981), often with no other shrub species present. Rackham (1994) considers that its ability to sucker profusely may have developed over time in response to the disease which has struck in past centuries.

Wych Elm Ulmus glabra Hudson (syn. Ulmus montana Loudon.)

Wych Elm Ulmus glabra is a broad spreading tree, the trunk usually forks into a Y shape. Sub-mature trees have smooth (hence 'glabra') silvery-grey bark which latter become fissured. The leaves are greater than 7cm in length; they are typically very rough on the upperside with more than 12 lateral veins covered in stiff white hairs, it has a short hairy petiole 2-5mm long, the leaves commonly have a three point apex; although this is not a diagnostic characteristic. It does not sucker freely, although it does coppice well (unlike English Elm U. procera). Wych Elm produces a mass of viable seed with relatively young trees reach fruiting maturity. Although it is vulnerable to Dutch Elm Disease senescence tends to occurs at a latter stage than English Elm U. procera. It is probably present in every 10x10 km square in the county. Wych Elm U. glabra is more tolerant of shady conditions and well adapted to northern climes where it is a major native component species of lowland mixed broad-leaved woodlands with Dog's Mercury (NVC W8) and lowland mixed broad-leaved woodlands with Bluebell (NVC WIO) in north-west England (Rodwell 1991). In Worcestershire it is an occasional component of such woods. It is often encountered in hedgerows, presumably because it was much planted.

Small-leaved Elm Ulmus minor Miller (syn. Smooth-leaved Elm Ulmus carpinifolia G. Sucklow and Ulmus nitens Moench)

Our rarest elm is the Small-leaved Elm Ulmus minor. Typically a tall tree with a narrow domed crown. Limbs in the upper crown are nearly all vertical, various size of branches ascend from the trunk, and unlike English Elm U. procera arch over to end in long pendulous branchlets with a narrow system of fine curled shoots. The bark has deep long, vertical fissures, commonly the branches have thick corky ridges. It has much smaller leaves than its counterparts being less than 7cm in length; although the leaf shape is extremely variable, they are most typically elliptic with the upper surface of the leaf being smooth and shiny green (Mitchell 1994). Where Small-leaved Elm U. minor is present it too is clonal i.e. produces suckers freely which are genetically identical to the parent plant. It is rarely attacked by the elm leaf-gall mite.

The status of Small-leaved Elm U minor within the county is so far undetermined. Its main centre of distribution is in the east of England which is why it is also referred to as East Anglian Elm. Small-leaved Elm U. minor is probably not native to Worcestershire with its presence being due to deliberate introduction. It is scattered along a 5 kilometre stretch of the A449 between Crossway Green and Ombersley.

Elm hybrids and immediate types

Unfortunately for those people studying elms (know as pteleologists!) there are a bewildering number of elm types. Rackham (1980) cites elms as being the most difficult critical genus in the British flora, Richens (1983) recognises 27 different forms in Essex alone. Intermediates between Wych Elm U. glabra and English Elm U. procera are uncommon and thought to be evolutionary i.e. without fixed characteristics (Rackham 1986). However, it is Small-leaved Elm U. minor which shows the greatest variation and it is this species which hybridises readily with other elms.

Hybrids and intermediate types in Worcestershire

Hybrid elms with fixed characteristic and other intermediate forms are uncommon in Worcestershire because of the scarcity of Small-leaved Elm U. minor. In places where Small-leaved Elm U. minor and English Elm U. procera are found growing in close proximity some suckers have characteristic common to both species. It is likely, as Rackham states, that such crosses are typically variable and can not be classified as true hybrids as they are probably still evolving. However, there are some elm hybrids in the county which show characteristics identical or very close to some of the forms presently described by Richens, Rackham and Mitchell. A very distinctive mature elm is present at Barnard's Green on the Guarlford Road, Malvern. Its growth form is identical to that of the Huntingdon Elm Ulmus x hollandica var. Vegeta (syn. Ulmus x vegeta), described by Mitchell 1994; as a tree with a regular tall domed crown with a straight clean bole. Its leaves are elliptic, long-acuminate, 10-13 x 8cm, doubly toothed with a petiole between 1-2cm. It was a tree that was very widely planted in the British Isles (Stace, 1991), however, only a few trees currently now survive (Mitchell 1994).

The most likely candidate for a naturalised hybrid elm is the so called 'Lineage' Elm which is specifically a woodland elm (Rackham, 1980). It has an intermediate leaf shape between Small-leaved Elm U. minor and Wych Elm U. glabra, but unlike the more familiar hybrid Dutch Elm Ulmus x hollandica it is non-invasive and coppices well. Lineage Elms are often found in homogenous stands and were probably deliberately planted in most situations. This tree is known to occur in Tiddesley Wood where it is locally common and may be scattered in other ancient woodland sites in Worcestershire. Whilst in the Lineage Elm and in some of the other hybrid combinations, phenotypic features can be reasonable determined, their true parentage can probably only be resolved as and when chromosomal analysis is undertaken*

Elm Trees and the Native Elm Programme

Elms grew taller than all other trees in the landscape with both English Elm U. procera and Small-leaved Elm U. minor regularly attaining heights of 120 feet (over 30 metres) or more. Elm wood is of medium weight and strength, but distorts easily and has to be seasoned carefully. Its timber was much valued in building construction and for use in furniture (Milner, 1992). Elm trees with circumferences of over 190cm are rare within the county. In 1996 a national survey was initiated by the Conservation Foundation with the aim of identifying elm trees which could be used for propagation of disease-resistant native stock. Small-leaved Elm U. minor is less susceptible to the disease than English Elm U. procera. In certain parts of Essex and Suffolk elm trees with circumferences of more than 150cm are still commonplace. Likewise some Wych Elms U. glabra reach full maturity and appear not to contract the disease.

So how many fully grown elm trees remain in Worcestershire? The answer is we do not know because we have no recorded data. However, we know of the existence of several Wych Elms trees, other still await discovery. One Huntingdon Elm Ulmus x hollandica var. Vegeta is present at Barnard's Green - are there others in urban situations? Recently a mature specimen of what is probably Small-leaved Elm U. minor was seen in a hedge to the north of Bewdley.

If we can find and record where our Worcestershire elm trees are distributed we will be able to replace elm trees using seed or cuttings from Worcestershire stock. If you are interested please pick up a copy of the Elm Newsletter in March 1998 at the Worcestershire Biological Recorders meeting.

* A phylogenetic reconstruction of the Ulmus genus based upon morphological and sequence data is being developed by Jayne Armstrong of the Division of Environmental and Evolutionary Biology at the University of Glasgow. This will provide a new taxonomic framework which could enable the comprehensive identification of hybrid elms and other forms within the county.


Armstrong, J, Gibbs, J, Webber, J, and Brasier, C. 1997. Elm Workshop Proceedings. Elm Newsletter No. 1. April 1997. The Conservation Foundation.
Mabey, R. 1996. Flora Britannica. Sinclair-Stevenson, London pp 58-62.
Milner, J.E. 1992. The Tree Book. (Channel Four Books) Collins & Brown, London pp 49-52.
Mitchell, A. Reprint 1994. Trees of Britain & Northern Europe. HarperCollins Publishers, London pp 247-253.
Peterken, G.F. Reprint 1994. Woodland Conservation and Management. Chapman & Hall, London.
Rackham, 0. 1980. Ancient Woodland. Its History, Vegetation and Uses in England Edward Arnold, Norwich pp 255 -281.
Rackham, 0. 1986. The History of the Countryside. J.M. Dent and Sons, London pp 232-247.
Rackham, 0. 1994. The Illustrated History of the Countryside. Orion Publishing Group, London pp 88-92
Richens, R.H. 1983. Elms. Cambridge University Press.
Rodwell, J. S. (Ed) 1991. British Plant Communities, Volume 1: Woodland and Scrub. Cambridge University Press.
Stace, C.A. 1991. New Flora of the British Isles. Cambridge University Press pp 137-141.
Wilkinson, G. 1978. Epitaph for the Elm. Hutchinson & Co. Ltd, London.

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