In the previous edition of the Tree Detective, I chose a tree that, while not as prominent as others near it, is definitely easily visible. In the recent heavy snowfall that transformed Exeter in a matter of hours, it was wonderful to see so many people of all ages play beneath the twisted boughs of the oak in Cowick Barton playing fields, and since the article was published, I have received many comments reflecting how much people love the tree.
This month, however, I have decided to focus on a more unusual specimen. It’s not at all old, it’s not in a public park, it’s not remarkably large (or small), and it’s not even native. So what is this tree and what makes it special? Hidden behind Cowick Street, on a stretch of green between Prospect Place and the back of the Methodist Church is a Foxglove Tree (Paulownia tomentosa). Originally from China, but now naturalised in much of the Southern United States and much of Southern and Central Europe, at some point one has found its way to St Thomas.
The Foxglove Tree, also called an Empress or Princess Tree, grows exceptionally fast, has flowers not too dissimilar to that of a foxglove, and also grows unusually large leaves. The species has accumulated an extraordinary and fascinating history in its travels around the world, bringing with it a weight of controversy and debate about its role in the different ecosystems in which it has appeared. In this edition of the Tree Detective I will take you on a journey stretching from the Miocene Era, more than 5 million years ago, through Ancient China and Japan, along the railroads of the industrial revolution and finally into the grounds of a 1960s/70s block of flats in St Thomas.
In February 1961, Charles J Smiley, an American palaeontologist published an article in the American Journal of Botany entitled A Record of Paulownia in the Tertiary of North America, Paulownia being the genus of the Foxglove Tree and the Tertiary describing a prehistoric period of time between 65 and 2.58 million years ago. Smiley asserted that the fossil record of the Ellensburg Formation in Eastern Washington, USA showed leaves clearly of the Paulownia genus dating from the late Miocene (11.6-5.3 million years ago) to the early Pliocene (5.3-3.6 million years ago). The significance of this is that the Foxglove Tree is treated as an invasive species, as its current natural population is in Eastern Asia. So is it really invasive if it has returned to the area from which it may have originated? At some point the tree became extinct in North America, probably because of the ice ages that repeatedly entombed much of the Northern Hemisphere. As such, it is more culturally associated with Japan and China.
Chinese legends imply a history of cultivation extending to perhaps more than 4000 years ago. Cross referencing conflicting pieces of cultural history is difficult, especially when one considers that the sources I’m reading are translations of a language that doesn’t always translate accurately into English. However it appears that when Yu the Great died and was buried on Kuaiji Mountain, Paulownia timber around 9cm thick was used to make his coffin. Meanwhile, in the philosophical prose writing of Zhuang Zhou (some time before 300BC), it is recounted that a Phoenix would not land on any tree other than the wu-t’ung (a type of Paulownia) when flying from the South Sea to the North Sea. In fact, there are scores of ancient records of the Foxglove Tree and its relatives in China, including everything from its cultivation, to its uses, to its cultural significance.
Across the sea in Japan, the tree dates back to at least 200AD. Japan is listed as part of the native range; however, it is more likely that naturalised populations have developed here as the species has been imported or spread from China. Nonetheless, it has been there long enough to embed itself in cultural tradition. In particular, a tradition that originated in Western China, but spread with the tree across China and into Korea and Japan, is to send a dresser made from the wood of an Empress Tree with a bride as she settles into her new marital home. The custom began by planting a tree at the birth of the child, so that by the time they reached the age of marrying, the tree was sufficiently large to be made into the piece of furniture. This custom was largely a tradition of the aristocracy, but the Foxglove Tree has made its way into even higher corridors of power, with the Japanese Prime Minister’s emblem depicting the leaves and flowers of the tree.
So far, what I’ve described is that of a wonderful, magical tree, that is adored by all; but, as previously mentioned, the tree is often regarded as invasive and destructive. If we are to understand this characteristic, we need to travel further forward in time to the age of industry and the railways.
As the railways rolled their way across China at the end of the 19th and the beginning of the 20th Centuries, people and plants travelled with the trains. It was common for people to stuff their packing cases with the light, fluffy seeds of paulownia trees, as they make excellent packing material. Often, packing cases would burst open, and the seeds would be scattered everywhere along the railway line. Very quickly, the Foxglove Tree made its way around Asia via train travel and became known as an invasive tree. Aside from where it had grown on plantations, it proliferated very quickly in the wild, and once it had been introduced into North America as a fast growing, strong wood supply, here too it became invasive. This brings us back full circle to the debate on whether it is native to North America, on account of its prehistoric origins there. However, that is a whole different article which I’m not really sure is the remit of Bloom In’ St Thomas!
If this tree really is so invasive though, why do we not see it all over St Thomas? Everything we have encountered thus far would say that it should have spread across the entire city. Certainly in many places in Europe, this is starting to happen. A warming climate has produced conditions more conducive to the spread of the Foxglove Tree. They are not, however, keen on harsh winters, and while adult trees are very capable of surviving cold weather, young trees fare less well in Northern latitudes. It is easy to forget how far north we are but, every so often, we get a period of exceptional cold that reminds us of this.
Another factor is the seeds. While the adult trees are very hardy and fast growing, the seeds are very susceptible to destruction by the fungi that live in the soil. Paulownia grow best on barren ground, where the soil is depleted of microbes and fungi, and are often early colonisers after forest fires. We have very microbe-rich soils and it is likely that most seeds would be killed because of this. I have planted a few seeds in a pot in my garden – at the time of writing they have not germinated, though if they do I will be sure to update this article accordingly. If my research is correct, however, they are not likely to grow in this manner. This means that the tree behind Prospect Place is very much a deliberate planting, however it is not the only one in the city. I am aware of at least one other example of the Foxglove Tree in Exeter; there is a specimen living below the terrace of Reed Hall on the Streatham Campus of the University of Exeter.
The work of the Tree Detective is never complete – there will always be more to learn about a tree, and by the time you think you’ve finished researching it, it’s older than it was when you started! As such, if you remember when this tree was planted, or have any other memories of it, get in touch. I’d love to know how old it is – I can only guess that it’s somewhere between 20 and 40 years old. Foxglove trees are incredibly fast growing, so it doesn’t take them long to get to a reasonable stature but this almost makes it harder to work out how old an individual is. I hope that one day, in a few decades time, I shall be able to write about this tree and remark that it is even older and larger, and that many more people came to know of it after this article.
Joe Levy (AKA the Tree Detective) is a resident of St Thomas who can be found wandering through parks and green spaces photographing trees or standing in the Precinct in all weathers handing out free food. Joe has been involved with Bloom’In St Thomas for more than 2 years and also sits on St Thomas Community Association as Youth Coordinator. Look out for a new edition of the Tree Detective every month!