We saw Mock Orange growing wild in Holyrood Park recently. Usually, it is found as a planted specimen in well-tended gardens and parklands, but it does sometimes grow wild. Gardeners like it because it provides an attractive shrub with fine flowers at the time of year when many other shrubs have stopped flowering. Also it has a powerful scent, attractive for some people but so powerful that others refuse to bring the flowers indoors.
Philadelphus growing wild at Holyrood Park, Edinburgh.
My father was trained as a gardener and he called it Syringa. But Syringa is the name for Lilac. The mistake wasn’t his alone; it seems to have started with Gerard’s Herbal of 1597 where two supposedly related species are shown side by side: they are labelled White Pipe and Blue Pipe and he calls them Syringa alba and Syringa cerulea. The word Syringa comes from syrinx, which in classical Greek music was a pan-pipe. The stems of both of these species are filled with pith and so could be made into pipes. But having pithy-stems is the only similarity. The two species are in completely different Families. Mock Orange (formerly Syringa alba now Philadelphus coronarius) is in the Hydrangeacae and Lilac (formerly Syringa cerulea now Syringa vulgaris) is in the Oleaceae (with Ash, Privet, Jasmine).
It is somewhat fanciful to think that stems of Lilac and Mock Orange are ‘pipes’. Here, an oblique cut has been made in one-year stems of Lilac (left) and Mock Orange (right). Mock Orange is more pipe-like than Lilac, but in both of them the central pith may be easily picked out to form a tube. Photo: John Grace.
Philadelphus coronarius comes from the Middle East. According to Plants of the World Online, it originates from a relatively small region in the world: North Caucasus, Transcaucasus and Turkey. It has however spread considerably because of its horticultural value as an ornamental species. It has often been recorded in North America and Asia, according to GBIF.
The story of its introduction to Europe begins with a Flemish man Ogier Ghiselin de Busbecq (1522-1592). He was a talented and highly educated individual who became a diplomat in the service of the monarchs of Austria. He was sent on a risky ambassadorial mission from Austria by the Emperor Ferdinand to the Ottoman Empire in Constantinople to resolve a territorial issue relating to the border with Transylvania. He dealt with the Sultan, known in the west as Soleiman the Magnificent, whose hobbies included growing tulips (hence their predominance in the design of Persian carpets). In between his diplomatic duties, Ogier Ghiselin de Busbecq was an avid collector, writing many letters and articles about the plants and animals he saw in Turkey. He took back plant specimens, possibly as a gift (perhaps a political ‘sweetener’) from Soleiman to Ferdinand, including Lilac, Philadelphus coronarius and tulips. What happened next?
Left: Ogier Ghiselin de Busbecq; right: Soleiman the Magnificent. Images from Wikipedia, open-source.
The distinguished Swiss botanist and physician Gaspard Bauhin (1560-1624) must have realised the confusion of Syringa and he called the species Philadelphus in his great book of 6,000 plants called Prodromos theatri botanici, and this name was adopted by Linnaeus in his Systema Naturae of 1735. We do not know exact dates of the introduction of the species to Britain but we know it grew in Gerard’s garden in 1597. Gerard had his own garden in Holborn, London where he “grew all manner of strange trees, herbes, rootes, plants, flowers and other such rare things”. Although he is criticised for plagiarising text from previous authors without attribution, he did often write descriptions ‘from life’ and this is probably one such case:
Later, in the 18th Century, other species of Philadelphus were brought from America and further confusion began. One of the others, Philadelphus inodorum is scentless. Other American species coming to our shores were P. pubescens (1800) and P. grandiflorus (1811). New species came from China and Japan, and several more from the Americas. They hybridise spontaneously under garden conditions, and so the ‘modern’ Mock Orange cannot be assumed to be the same as the original Philadelphus coronarius. For this reason, many plant recorders are reluctant to call the wild Mock Orange Philadelphus coronarius but simply write Philadelphus. Most of the ‘modern types are creations of the French plant-breeder Victor Lemoine of Nancy (1823–1912). Some of them are described and illustrated here.
In the 19th century various hybrids arose spontaneously in gardens. Notable hybrids were between the Old World P. coronarius and the American P. inodorus and P. pubescens. Some of these are treated as species. Modern hybrids are mostly the result of deliberate crossing, the creations of the great French plant-breeder Victor Lemoine of Nancy (1823–1912) or of his successors.
Bean’s Trees and Shrubs Hardy in the British Isles says of Philadelphus: “Perhaps no genus of shrubs presents so many difficulties in the differentiation of its species as this”. The book goes on to describe some 20 species in detail. It then turns his focus to “The Lemoine and other modern hybrids” of which he finds as many as 22. The task of identification is therefore daunting. Only nine are recognised on the BSBI/Maps page. A local expert has tentatively identified the one in Holyrood Park as one of the lemoinei cultivars (how disappointing – I wanted it to be Philadelphus coronarius).
How did Philadelphus escape into the wild? Normally, in garden conditions, it spreads vegetatively by ‘suckers’ from the root system (the one at Holyrood Park is doing this). It does set seed, at least sometimes, but I can find no information about its dispersal. Probably garden throw-outs and soil containing root fragments are the origins of many wild records. The first British record from the wild was in 1919.
Distribution of Philadelphus in Britain and Ireland, from BSBI. See also the entry in the BSBI’s on-line Atlas. Note: the species is concentrated around areas of higher population density.
Looking at the modern BSBI records from Lanarkshire and Midlothian we may make the following inferences. (i) Many records are in parks and probably these are planted specimens (eg from Lanarkshire: ‘Garden Festival Site’ and from Midlothian: ‘Astley Ainslie Hospital’). (ii) Other sites are unlikely to represent planted specimens, for example from Lanarkshire we find: ‘Proven Gasworks’ and from Midlothian: ‘Monktonhall Bing’. Likewise, Trueman et al. (2023) compiled records from Sutton Park in the urban West Midlands of England, sometimes from habitats which were also unlikely to have been planted: railway embankments, post-industrial waste-land and a marsh.
Philadelphus coronarius. Native range (green) and introduced range (purple), from Plants of the World Online.
I have attempted to find references to the species in its native range. In one paper (Novák et al. 2020) on oak-hornbeam woodland in the Caucasus it is said:
“The tree layer is mostly dominated by noble hardwood tree species, mainly by typical species of the warm parts of Eastern Transcaucasia (Acer velutinum, Tilia begoniifolia). Other noble hardwood tree species commonly occurring in the previous community are less common or even absent (Acer platanoides). The shrub layer is formed by mesophilous species, Corylus avellana and Sambucus nigra reach the highest cover. Philadelphus coronarius, frequently colonizing shaded scree slopes, is highly diagnostic for this community”.
The Holyrood Park situation is not dissimilar to Novák’s example: the Holyrood site is shaded and has both Corylus avellana (Hazel) and Sambucus nigra (Elder).
In the USA there are several species of Philadelphus, widely used as ornamentals and for borders, screens, hedges and recreational planting. Details of their cultivation and propagation have been well worked-out, and they are routinely produced in nurseries by seeds and cuttings. Historically, Philadelphus has been widely used by the indigenous people of North America to make baskets, cradles and arrows. One of them, P. lewisii is the State Flower of Idaho, where it is valued for its versatility, but still often called Syringa. More information from North America can be found here. Worldwide, the genus Philadelphus contains around 60 species including many in Asia, while the World Plant List, which includes all known cultivars, lists several hundred taxa. Only the bravest taxonomists have tried to sort them out and provide keys. Hu Xiuying was from China; she studied at Harvard University and anyone who wishes to delve deeply into the genus should study her remarkable 1954 monograph.
I wondered whether Philadelphus has medicinal value, having seen a research paper which emphasises its antimicrobial properties. Looking for an independent view in an area where I have no professional expertise, I found a new way to enquire. I turned to the Artificial Intelligence (AI) software from Google called Bard. I am an ‘early user’ and Google quietly tells me to be cautious as Bard sometimes gets things wrong. However, I asked Bard about the medicinal value of the plant and the reply was:
“There is no scientific evidence to support the use of Philadelphus coronarius for medicinal purposes. The plant has been used in traditional medicine for centuries, but there is no evidence that it is effective in treating any medical conditions”.
I will report further on Bard’s progress. When I asked Bard about myself it made serious errors. Next, I’ll test it on crossword clues.
References
Bean WJ (1986) Trees and Shrubs Hardy in the British Isles, 8th edition. Murray, London.
Coats AM (1963) Garden Shrubs and their Histories. Vista, London.
Hu SY. 1955. A monograph of the genus Philadelphus. Journal of the Arnold Arboretum 36: 52B109
Novák P et al. (2020) Ecology and vegetation types of oak-hornbeam and ravine forests of the Eastern Greater Caucasus, Georgia. Folia Geobot 55, 333–349. https://doi.org/10.1007/s12224-020-09386-0
©John Grace
Botany in Scotland 