Platanus × hispanica Mill. ex Münchh.

Origins

In western Europe in particular, Platanus × hispanica is one of the most important of ornamental trees, as well as being among the largest and longest-lived. But for such a conspicuous plant its origins remain surprisingly obscure, and it is only in the 21^st century that its nomenclature seems finally to have stabilised.

The German botanist Otto von Münchhausen published today’s generally preferred name Platanus [× ] hispanica in 1770, basing this on a 1759 description by Philip Miller, chief gardener at the Chelsea Physic Garden in London, of a ‘Spanish Plane’. (As such, this tree was presumably felt to be distinct from the hybrids which seem already to have been growing in England.) The tree in the Chelsea Physic Garden has long gone and this ‘Spanish Plane’ cannot be matched with any confidence to any variants now in cultivation; Henry & Flood (1919) believed that it represented the clone known today as ‘Augustine Henry’, a form certainly recalled by Miller’s description of five deeply-toothed lobes to the leaf, but there is perhaps too long a gap between Miller’s record and the appearance of today’s ‘Augustine Henry’ at the Van Houtte nursery in Belgium in the 1870s – where it was in any case being mis-sold as the Californian species P. racemosa.

Until very recently, a popular alternative name to Münchhausen’s was P. [× ] acerifolia, published in 1805 by another German botanist, Carl Ludwig Willdenow, and based this time on a 1789 description by William Aiton of a tree at Kew, once again in London. Aiton had called this tree ‘Spanish Plane’ too, raising the possibility that he was aware of the Chelsea Physic Garden tree and felt it was the same, although Willdenow does not describe the multi-toothed leaves of Miller’s ‘hispanica’ (Aiton 1811; Willdenow 1805). Carl Ludwig Willdenow (1765–1812) was an early proponent of phytogeography, felt obliged in his work Linnaei species plantarum (1798–1826) to offer a natural distribution for each species he was describing, also contradicted Aiton by claiming that this tree was from the Orient (Willdenow 1805). The example on which Aiton and Willdenow’s descriptions were based is very likely to be the plane which still survives in the Rhododendron Dell at Kew; tradition supposes that this tree is contemporary with Capability Brown’s landscaping of this area in 1773 (Bean 1976), and its steady growth through the 20^th century supports this idea, implying that it should have been known to Aiton. There is no documentary evidence that any other London Planes as old as this have ever been lost at Kew, and the only other planes at Kew which Aiton described were three other variants assumed to belong to Platanus orientalis and as such distinguished by their cuneate rather than truncate (to cordate) leaf-bases – one of these Oriental Planes still survives near Kew Palace – and also a P. occidentalis, long gone but confirmable from contemporaneous herbarium specimens. Willdenow’s description of five-lobed leaves resembling those of Silver Maple (Acer saccharinum) would fit the foliage of the current tree in the Dell, although it would also fit many other clones. The Kew tree belongs to a rather scarce but easily recognised variant of the hybrid, which is accordingly described below as the cultiver ‘Acerifolia’.

The year before Willdenow published the name P. [× ] acerifolia, the Portuguese botanist Félix de Avelar Brotero had provided a third potential name by describing a P. hybridus [sic], which also showed features intermediate between those of P. orientalis and P. occidentalis; a specimen in Willdenow’s herbarium provides a close match to a couple of trees growing in Toulouse in the later 20^th century (Bean 1976).

Perhaps less contentious is the vernacular name ‘London Plane’. Wherever the hybrid first occurred, Platanus × hispanica went on through the later 19^th and earlier 20^th centuries to become London’s most planted street tree, coping with very poor air quality and thriving incomparably in this city’s combination of relatively long and warm summers – for England at least – and generally heavy but fertile, riverine soils. In 1920, Angus Webster estimated that two thirds of the trees being planted in public places across the city were London Planes (Webster 1920). Today, cleaner air allows a huge variety of tree species to flourish within the capital and planting has slowly become much more diverse, yet, in terms of tonnage at least, London Planes still dominate overwhelmingingly. They include all of the city’s tallest trees, with specimens of 40 m at St Paul’s Cathedral churchyard, in the historic garden of Finsbury Circus, and beside the Thames at Petersham; these must in fact be among the tallest and most impressive of all urban specimen trees (Tree Register 2025). For this reason, the following account is unrepentently anglocentric in its treatment of this hybrid, but the importance of this tree is demonstrated by the vast numbers planted all round the world.

Two small plants of Platanus occidentalis, the hybrid’s American parent, were growing in John Tradescant the Elder’s garden, ‘The Ark’, at Lambeth (now in south London) by the 1630s (Gerard & Johnson 1633); the Eurasian parent, P. orientalis, was probably shedding its pollen from planted specimens quite widely across England by this period. From not far away at the Oxford Botanic Garden (then the Oxford Physic Garden), a manuscript by the Keeper, Jacob Bobart the Younger, undated but assumed to be from the 1660s, described three different planes: P. orientalis, P. occidentalis and one ‘halfway between the eastern and the western’ (Henry & Flood 1919; the author’s translation of Bobart’s original Latin). A foliage specimen, evidently taken from this intermediate tree and labelled ‘Platanus media’, survives in the Sherard Herbarium at Oxford, while another was collected by James Petiver around the same time; these specimens were considered by Augustine Henry to represent ‘undoubtedly P. acerifolia’ (Henry & Flood 1919; this is not to imply they felt it was the same as the Kew tree here described as the clone ‘Acerifolia’. As was then the mode, Henry used P. acerifolia for the whole nothospecies). In 1700 Leonard Plukenet also described a plane in the Oxford Botanic Garden ‘with an appearance halfway between the eastern and the western planes, American in origin, with larger fruit-balls and dark, shining foliage’ (Henry & Flood 1919; the author’s translation of Plukenet’s original Latin). Since Bobart’s description never made it into print, and long predates the Linnaean concept of binomial nomenclature, ‘Platanus × media’ unfortunately cannot be adopted as the London Plane’s earliest and least equivocal botanical name. ‘Media’ is, however, recommended here as the earliest available and least confusing cultivar name for the assumed descendants of this original cross.

Whether the Oxford tree – with its supposed American origin – really represented a hybrid was questioned by W.J. Bean (Bean 1976). Bean argued that Platanus occidentalis seemed impossible to grow to flowering age at Kew in the early 20th century, and so will not have been at all likely to have crossed with P. orientalis in 17th century London or Oxford. More recently however, P. occidentalis has successfully been grown in climates including that of the Royal Botanic Garden Edinburgh – where summers are probably still cooler and shorter than they were in London during the height of the Little Ice Age; for a species with such a wide natural range, provenance is presumably important. Furthermore, Bean described a herbarium specimen of genuine P. occidentalis bearing a mature fruit-ball which had been collected, almost certainly at Kew, by Samuel Goodenough (Bishop of Carlisle and amateur botanist) late in the 18th century. Bean’s speculation that the earliest hybrid planes in England must instead have been imported from somewhere in southern Europe, as Miller’s and Aiton’s ‘Spanish Planes’ may have been a century later, seems to fail the test of Occam’s razor; there is no documentary evidence for P. occidentalis being cultivated anywhere outside England at a sufficiently early date. For example, the American species is only supposed to have been introduced to France by Georges-Louis Leclerk, the Comte de Buffon, in the mid 18th century (Geerinck 1998), and the largest examples known today on the Continent, whilst huge and flourishing, seem likely to date only from the 19th century (Monumental Trees 2025). Bean also suggested that the leaves in the Sherard Herbarium at Oxford could have belonged to P. occidentalis, but most observers will probably agree with Augustine Henry that their five distinct and quite deep lobes are a good indication of hybrid origin and that they resemble the commonest form of older hybrid plane in London today; the remarkable variability of London Plane leaves, from different parts of the same tree, from the same tree as it matures, and from early or later growths, make it hard to be more certain.

Bobart’s original ‘Platanus media’ no longer survives at the Oxford Botanic Garden: if it had, it would now monopolise much of the site’s 1.8 ha. Nor can we be completely confident that any surviving trees are its direct descendants. A huge plane a couple of hundred metres away in front of the New Building at Magdalen College, 33 m tall and with a dbh of 2.4 m in 2009, is stated on its (modern) plaque to have been planted in 1801 as a scion of the Botanic Garden tree, and also seems typical of the commonest form of the hybrid in London – but it is possible that this statement was simply a nod to the ongoing assumption that most London Planes descend ultimately from the Oxford tree. Hearsay also proposes a 17th century origin to a plane of very similar appearance at the Bishop’s Palace in Ely (33 m × 2.93 m in 1997), which is supposed to have been a gift from King Charles II to Peter Gunning, the Bishop here from 1674–84. Nearby, at Buckden Towers, two more planes of the same sort, the larger 34 m × 2.46 m in 2012, are claimed to have been planted as early as 1660 by Robert Sanderson, the Bishop of Lincoln. Henry & Poole (1919) suggested that lost specimens at Woolbeding in West Sussex and at Peamore in Devon were equally old, on the basis of their stature, while another gigantic plane, again similar in appearance, at Barnes in west London (35 m × 2.68 m in 2017) is often taken to be contemporaneous. Another similar plane at Wotton House in Surrey (26 m × 2.22 m in 2013) is reputed to have been planted by John Evelyn, around the time that he inherited this estate in 1699. Recent remeasurements of the surviving trees from this cast show that they are all growing strongly and thus could reasonably date from the mid-18th century, along with various other London Planes found more recently in England that are now even bigger (Tree Register 2025). Since all of these trees retain much of the vigour of youth, it could, conversely, be argued that they should be growing faster now than they will have managed in the short summers of the Little Ice Age in the 17th and early 18th centuries. The location of the Barnes tree means that it is in reality unlikely to antedate the creation of a garden here by Sir Henry Hoare in 1752–54; but there are no compelling reasons to reject the claimed 17th century planting dates of the other examples.

It therefore seems reasonable to assume that all of these earliest English plantings, along with a preponderance of the mature plane-trees in London, are the direct descendants of Bobart’s ‘Platanus media’; DNA fingerprinting might in due course cast light on this question, or else reveal a more complex picture, but it should be remembered that earlier analyses failed even to differentiate P. × hispanica (in general) from P. orientalis (Grimm & Denk 2010). This variant has never acquired a satisfactory cultivar name, being described (if at all) as ‘London’ or just as ‘London Plane’; below, it is discussed further under the earliest available name, ‘Media’.

Although Monumental Trees (2025) lists plenty of apparently hybrid plane-trees in continental Europe believed to be as much as 475 years old, these claims manifestly originate in naive estimates based on the trees’ impressive girths. Even the apparently precise 1668 planting date for a plane in front of Oelzschau Castle in Germany seems derived from the age of the Castle itself, which was completed in 1669. The largest are comparable in stature and also in apperance to the biggest and oldest specimens in England, and might reasonably date from the early or mid 18th century, as scions of the Oxford ‘Media’; indeed, it needs to be borne in mind that the longer and warmer the summer, the faster a London Plane is liable to grow.

The earliest survey of London Planes in Britain and Ireland was published by J.C. Loudon in Arboretum et Fruticetum Britannicum, utilising the measurements and the estimated ages sent to him by numerous estates between 1835–37 (Loudon 1838). Loudon classified them all as Platanus occidentalis – to indicate, at least, that they seemed to differ from the more familiar P. orientalis; as most were either big or vigorous trees, subsequent commentators have assumed that none of them represented true P. occidentalis. The oldest of Loudon’s trees, at Castle Ward in Northern Ireland, was known or more probably estimated to date from around 1705. It is instructive, if disappointing, that only four of these 22 trees can reasonably be matched to surviving specimens (Tree Register 2025: at Biel in East Lothian, Dodington Park in Gloucestershire, Haffield in Herefordshire and Nettlecombe in Somerset); none of the specimens which are nowadays believed to represent the oldest happened to make it onto Loudon’s shortlist. Although the giant plants at Ely, Buckden Towers and Wotton do not give an appearance of being ancient, or even middle-aged, Loudon’s list should also remind us that no tree is immortal and that plantings can die, or blow down, or be removed for any number of reasons; when the original tree disappears, the legends surrounding its origin can potentially get transferred to a replacement plant.

Cultivation and plant health

For a fuller treatment of the pests and diseases affecting London Plane, see the sections ‘Pests and Diseases’ in the genus article. The most serious threat is posed by the fungal infection Canker Stain Disease (CSD), when tends to kill specimens of the European parent P. orientalis within a year or two, but to which the American P. occidentalis generally survives; the hybrids vary in their susceptibility, and some clones are planted, in the United States and southern Europe, for their proven ability to withstand CSD. Given thorough (and expensive) sanitation measures, outbreaks of CSD are proving – as in the case of Switzerland – to be containable, and the disease has yet to be reported from the UK. So far, its effects have been most severe in southern France, Greece, Albania and Turkey (Tsopelas et al. 2017; Forest Research 2025).

The endemic presence of CSD in eastern North America will have contributed to the significantly less illustrious history of Platanus × hispanica as an urban tree in the United States. A major outbreak of CSD in the north-eastern States in the 1940s killed 87%, for example, of the London Planes planted in Gloucester, New Jersey (Wikipedia 2025), although the disease’s impact in North America has since then inexplicably declined. It is certainly not the case that the native P. occidentalis has been preferred in America; this is a plant adapted to a woodland ecology and which is less suited to withstand the rigours of city life (Jacobson 1996). Plane Anthracnose, another fungal infection, is seldom fatal but can defoliate susceptible trees and is wind-borne; P. occidentalis has no natural immunity, and infected wild populations present a constant source of cross-infection for planted P. × hispanica, so that American nurseries have felt it more important to select for anthracnose resistance in London Plane clones. Another demerit to the use of P. × hispanica in the United States is its tendency to hybridise with native Platanus species, diluting their genes; this is particularly true in the Los Angeles area, where crosses with the native P. racemosa are themselves fertile and form a spreading population (Council for Watershed Health Invasive Plant Monitoring and Outreach Program (Weed Watch) 2007).

Platanus × hispanica only performs at its best within a relative narrow climatic band. London is, in fact, currently at the northern edge of this zone; had the capital city been located on a river in northern England, we would probably have ended up with a London Poplar or a London Willow instead. In Britain, the northernmost really impressive historic planting of London Planes is probably J.C. Loudon’s from the late 1830s in the Derby Arboretum, at a low elevation in the English Midlands. There are a few very big trees in the warmest parts of Ireland and Wales, including one 2.5 m dbh at Tourin Castle in Co. Waterford in 2010 and a magnificent tree 2.25 m dbh at Llanover Park in Monmouthshire in 2017; the Scottish champion (1.87 cm dbh in 2019) grows in the far south-west at Kirkconnell, neatly very near to the spot which must accumulate the greatest number of degrees of warmth per annum in Scotland (Tree Register 2025). Following damaging storms in the early 2010s, Edinburgh City Council planted London Planes quite widely through the city; many were injured by late frosts in the early years but a few are now beginning to develop into respectable young trees, though with nothing like the vigour one would see further south and none serve as ambassadors for their kin (T. Christian pers. comm. 2025). London Planes currently seem to reach the southern limit of their comfort zone in the subtropical climate of central Florida (Dirr 2009).

Most London Plane clones are easily raised from cuttings, unlike the parent species; another way of putting this would be that it was seedlings which nurseries found easy to propagate – such as ‘Pyramidalis’ – that have become widely planted. Hardwood cuttings 20–30 cm long taken in the autumn will root over winter, or can be taken early the following spring, rooting almost immediately. Softwood cuttings can also be successfully rooted from June onwards (Chengappa 2022). Nurseries also used to layer shoots from parent stools (Bean 1976). The attractive clone ‘Augustine Henry’ is relatively hard to root from cuttings, and may be sold as a graft, or ‘nurse-grafted’ by grafting it onto a temporary rootstock which is later removed (Chengappa 2022).

In suitable conditions Platanus × hispanica can self-sow freely, producing populations of individuals clearly referable to this hybrid. This is very striking along the banks of the Tiber in Rome (see image), where thickets of plane saplings have sprung up below the avenue of clonal trees on the embankment above (J. Grimshaw pers. comm. 2025). In the British climate self-sown specimens are rarer, but in the hotter south-east Platanus seedlings can often be found in pavement cracks and against walls. At one time there was a a fine crop of them below the window in Sub-Basement A of the Kew herbarium where Ross Bayton sat while working on New Trees, but this has long being removed by herbicides (J. Grimshaw pers. comm. 2025). Whether these included seedlings from nearby P. orientalis or backcrosses between the two taxa is unknown, but the BSBI Plant Atlas 2020 records that seedlings of P. × hispanica are common in urban areas, whereas those of [P. orientalis] are much scarcer (Stroh et al. (eds) 2020). It would be worth careful observation of spontaneous plane seedlings to ascertain which taxon they belong to.

Identification and characteristics

The variability of hybrid seedlings can make it difficult to distinguish these from either parent Platanus species. As a guideline, the foliage of P. orientalis remains a fresher and paler green through summer than those of hybrids which share leaves with five deep lobes, and this feature can be particularly easy to spot in aerial imagery taken in a good light. The volatile oils in the foliage of P. orientalis are sufficiently abundant to scent the air around the tree through summer, which is very seldom the case in hybrids, although it has to be admitted that the hybrids are much more likely to be found in places where the odour of exhaust fumes overwhelms everything else. Generally, the habit of P. orientalis tends to be lower and broader. The fruit-balls of the American P. occidentalis (usually carried singly, which is less commonly true among the hybrids) appear slightly less spiky, since the style breaks off each seed through summer to leave a stub which only projects about 1 mm from the body of the ball; in hybrids the 5–7 mm style tends to persist until autumn or winter.

With the exception of a few Eucalyptus species, Platanus × hispanica makes Europe’s tallest broadleaved trees; with the exception of the Larch, Larix decidua, they are also the continent’s tallest deciduous plants, surpassing 52 m in the favourable conditions of Pau, in the shelter of the Pyrenees in south-western France (Monumental Trees 2025). The UK’s tallest broadleaved and deciduous trees are a group of unusually long-stemmed and clean-limbed London Planes at Bryanston House in Dorset, which are supposed to date from about 1740; the tallest is currently just shy of 50 m (Tree Register 2025). The Bryanston trees may belong to the clone described below as ‘Acerifolia’, although their unique vigour could imply genetic differences.

The tendency to grow a longer bole and a higher and slenderer canopy than typical specimens of Platanus orientalis helps to fit London Planes among tall buildings, although it must sometimes have been the case that these boles result from early formative pruning. London Planes are remarkably docile when pollarded each winter, or every few winters, but it could certainly be argued that, if they need such drastic treatment to keep them within their allocated space, smaller-growing trees would have been a better choice. The extra-vigorous growth that results from hard pruning is more vulnerable to minor damage in summer from powdery mildew and from summer squalls (Chengappa 2022). London Planes have a reputation as one of the safest trees for much-frequented places, seldom shedding branches and even more rarely blowing down, but Massaria infections, due to the fungus Splanchnonema platani, result in sudden branch loss; the global spread of this disease has necessitated regular and costly safety inspections, and could, it is feared, contribute to authorities preferring to plant lower-maintenance tree species in future (Forest Research (ed) 2025).

It might be argued that, to fulfil its role in softening the outlines of tall buildings, purifying polluted urban air, casting cooling shade in summer and baffling cold winds in winter, a street tree should be large enough to fill the space available for it. In particular, the starry hairs that cover the younger foliage of London Planes are excellent air filters (Baldaccini et al. 2017), a role which more than compensates for their irritant effect on human lungs as they – plus the hairs on the seeds – are shed and blow in the wind. (Cold comfort to sufferers, of course!) In common with many massive trees, London Planes (at least in the variant ‘Media’) ultimately develop strongly flared trunks, resulting in raised paving stones and cracked tarmac; it is always better to plant them on grass and in shrubberies rather than in pavements themselves, even though the roots themselves seem remarkably tolerant of hot, compacted ground. Many of London’s largest planes are to be found within the city’s residential garden squares; a few monumental street trees include one of 30 m × 5.2 m dbh (in 2018) which occupies most of the pavement of Christchurch Hill in leafy Hampstead (Tree Register 2025). The specimens which seem to have set the fashion for planting planes in London’s squares are the 25 or so survivors from the original landscaping of Berkeley Square, Mayfair, a scheme instigated by Edward Bouverie in or around 1789.

Aesthetically, London Planes are among the few trees which come into their own in winter – exactly when the London climate most needs cheering up. As climate change warms our summers, the cool shade created by their tall, densely leafy crowns will be valued more and more, but the leaves themselves tend to be a curiously heavy rich green, and are too large to appear graceful en masse. In an English autumn, they also fall with very little colour. Leafless, however, the finely-flaking pale and multicoloured upper trunk and branches are revealed, along with the strange logic of the twisting high limbs of ‘Media’ and ‘Acerifolia’ and their unexpectedly delicate cascades of fine outer shoots. The fruit balls with their irritant hairs are abundant in only a few clones such as ‘Palmata’ – another advantage to other forms of the cross over its parents – but they add extra interest to the twiggery as they hang on through the winter months.

London Planes are also unusual among trees in growing more graceful as they age. Youngsters can have a straggly habit, with their leaves appearing too large for the tree itself; this can lead to fears that today’s clones are inferior to those planted two or three hundred years ago. One reason for presenting clonal names in this account, often for the first time, for a range of the older forms is to encourage the propagation and perpetuation of these historic plants.

All trees can be untidy; most planes, although they seldom shed limbs or branches when healthy, are continually sloughing thin scales of bark. Bean (1976) suggested that this happens particularly in high winds, presumably because the flexing of the limbs and trunk dislodges any loose flakes, while Mitchell (1996) observed that during the severe drought of 1976 in England, ‘planes shed piles of big, hard, curved plates from the bark making walking under them very difficult’. The leaves, being quite thick and hard, rot down slowly, making them relatively easy to sweep from street gutters, but somewhat troublesome until this task is done.

One peculiarity of Platanus trunks is the readiness with which the timber flows around, or inosculates with, adjoining objects. The infamous ‘hungry tree’, a London Plane at the King’s Inns in Dublin, Ireland, is halfway through swallowing the park bench which it used to shade. In Britain, Royal Mail letter-boxes seem to be part of these trees’ staple diet, with conspicuous casualties in Ninian Road, Cardiff, Wales, and in Drayton Gardens, London (Wood 2025). At Mottisfont Abbey in Hampshire, England, a drawing by J.C. Buckell in 1822 shows two planes planted in picturesque contiguity on the lawn beside the river Test, which were then perhaps as much as a hundred years old. ‘Bundling’ trees or planting close clumps was a fashionable way of creating an ancient-looking landscape, but only in the case of London Planes, perhaps, were identical twins thus bundled together (in this case the clone ‘Media’). By the time that Augustine Henry visited Mottisfont in 1898, the trunks had fused and Henry imagined that here was one tree with a low fork (Elwes & Henry 1906–1913), as have numerous dendrologists ever since; the single bole created by these arboreal twins is now more than 4 m broad. Unusually for the hybrid, which is often planted in tight urban places where there is no opportunity to behave in this fashion, the southern tree of the Mottisfont pair has also spawned a large layer, which now forms a separate leaning tree about 15 m away from its parent. By the town bridge in the centre of Bradford-upon-Avon in Wiltshire, a slightly younger pair are at an earlier stage of fusion; Alan Mitchell had been able to measure the trunks separately in 1985 but on the day of the author’s visit it would only have been possible to do this by draping the tape-measure over the back of a somewhat complacent Mallard duck who was nesting on top of the parapet of timber that unites the stems (Tree Register 2025). At the Deanery in Winchester, Hampshire, and by the Thames at Petersham in west London, two other close pairs remain more or less separate, for now. The Petersham trees represent the scarcer clone ‘Acerifolia’, which since its bole becomes less flared may not be so prone to inosculating in this way; here, the pair of trunks also have facing hollows, perhaps indicating where a third component member of the clump has failed. The roots of London Planes can also fuse readily with their neighbours’, increasing the risk of CSD infecting one tree after another in lines or avenues.

Some unnamed variants

It is possible to recognise clonal populations within species that are generally reproduced by cuttings or layers, but which are also fertile; this is certainly true of the London Plane, whose seedlings can be remarkably diverse in appearance (Henry & Flood 1919). Until now, only a few of these variants have gained more or less stable clonal names; these are discussed below as cultivars (‘Augustine Henry’, ‘Pyramidalis’, ‘Palmata’). In addition, this account proposes ‘Media’ as an occasionally useful name for the population which seems likely to derive from the original, Oxford cross, ‘Acerifolia’ for the clone which seems to have been described by Willdenow as Platanus acerifolia, and a Baobab Group for hybrids with disproportionately swollen lower boles. Careful study of the hybrid planes which have been planted in other countries might well, of course, add to this case of clones.

‘Palmata’ and Baobab Group trees seem likely from the shape of their leaves to be among the seedling progeny which arose as back-crosses with Platanus orientalis. Phylogenetic studies of some modern London Plane clones from Sweden and Austria (at least) have shown that these are much closer to P. orientalis than they are to P. occidentalis, as a result of repeated back-crossing with the European parent (Grimm & Denk 2010). Modern first-generation crosses, raised under controlled conditions, include the clones ‘Columbia’ and ‘Liberty’, bred by Frank Santamour at the United States National Arboretum in the late 1960s.

Anyone observing the population of hybrid planes where these trees have long been planted in abundance will find trees that differ from any named clone and which were presumably raised from seed; Chengappa (2022) provides extensive notes on such trees around London, including a sport in Eastern Avenue, Romford, with yellowish younger foliage.

The author Paul Wood has also noted a population of London Planes with particularly zig-zag major limbs, citing a representative specimen at the corner of St Giles and Keble Road in Oxford (Wood 2024). Sadly, Wood’s suggested name ‘Spiralis’ lacks any documented history, and its latinate form would make it illegitimate as a new cultivar name. This variant should perhaps not be confused with ‘Tortuosa’, described by Loudon 1838 as a seedling of Platanus occidentalis (under which name Loudon also described today’s London Planes) with a ‘stem full of knots, which renders the fibres tortuous, and, consequently, difficult to split.’

A variety minor was described by the Italian botanist Michele Tenore from a tree at Caserta, Italy, with very small leaves and scarcely-toothed lobes; (Bean 1976) compared this with a stunted, small-leaved tree in the Syon Vista at Kew Gardens which had come from the Van Houtte nursery in Belgium in the 1870s. A similar tree (but with leaves described as truncate at the base, rather than cordate) was named P. cantabrigensis by Augustine Henry (Henry & Flood 1919) from a tree at the Cambridge University Botanic Garden; Henry observed that the seeds seemed infertile, an indication of hybrid origin. What is supposed to be Henry’s specimen still grows in the Botanic Garden but ‘does not appear to be significantly distinct’ (Chengappa 2022). The mis-spelling ‘cantabrigiensis’ is sometimes encountered.