Just before the gap in the walls that leads to the lower garden there stands a large English yew tree (Taxus baccata). Planted in 1645, it is the oldest living thing in the Botanic Garden – the walls are older, but nothing else can match it. When it was planted, the Garden had only been open for thirteen years (though it was founded eleven years before that), and its director was Jacob Bobart the Elder. In 1648, not long after getting his yew tree, Bobart created a list of all the plants in the Garden, entitled Catologus plantarum Horti medici Oxoniensis (catalogue of the plants in the Oxford medicinal garden). It contains approximately 1400 plant names, and several of these species are now grown in the 1648 border in the south-west corner of the Walled Garden.

As you would expect in a medicinal garden, the plants in the seventeenth-century Garden were often thought to have medicinal uses – tutsan (Hypericum androsaemum), for instance, gets its common name from the French for ‘all healthy’. Not every plant was thought to cure the sick, though – Buxus sempervirens was used to make hedges, and the yew tree was planted to look good. The plants in the Garden were also a mixture of native and non-native species. For visitors in 1648 the most exciting and exotic plant currently in the border would have been the Virginian spiderwort (Tradescantia virginiana). Sent from the east coast of America to a collector called John Tradescant some twenty or thirty years before, it would have been found in only a few gardens around the country and certainly not in the wild – the majority of visitors would never have seen it before.

When the Garden was established, part of its founding aim was “the glorification of God”, with the collection and display of rare and interesting plants used as a way of achieving this. However, the Garden is now – and in fact always was – about much more than just ‘trophy hunting’ plant species. The second half of the Garden’s mission statement was that it should be used “for the furtherance of learning,” although it seems that you had to be one of a very fortunate few to benefit. Even in the 1850s, two whole centuries after Bobart’s catalogue was published, the Garden did not present a very friendly exterior. The main entrance was kept locked and you had to ask to be let in – the same was true with the glasshouses. Even then, it wasn’t as if just anyone could be allowed to enter: orders had long been in place “to exclude nursery-maids and children from the premises.” (You will be pleased to know, if you hadn’t already noticed, that this is no longer the case.)

The Botanic Garden would originally have played a major role in the education of medical students, on how to make cures from useful plants and which ones to avoid (there are several of both types in the 1648 collection), but it also has a long history in other scientific research. For example: in the seventeenth century plant reproduction was very poorly understood – flowers were thought to be solely decorative, and some seedless plants, like Dryopteris filix-mas, would have been a complete mystery. In the mid-1670s, Oxford’s Professor of Natural Philosophy, Sir Thomas Millington, proposed that the parts of the flowers that were then called ‘the attire’ (what we now call the stamens) “served as the male for the generation of the seed.” He was absolutely right, and well ahead of the time; and to cap it all off, it seems very likely that he gathered the evidence for his conclusions in Bobart’s Botanic Garden.

These days the Garden is still used for research and education but, much like the Garden itself, they are now available to anyone. The information on the 1648 collection can teach you something about the changing make up of the Garden, as well as highlighting the differences in the way plants were viewed then and now. Walking around the Garden you will find that many of the plants have information about their uses on their labels, and the emphasis on plants in medicine has not been lost, although it is less dominant than in centuries past. This fascinating aspect of plant science can be seen in the medicinal plants trail, which features Bobart’s yew, as well as the medicinal plants beds which sit opposite the 1648 border. In the early years, many physic gardens (although, interestingly, apparently not Oxford’s) actually did more than just educate students about plant-based medicines – they manufactured and sold their own. For many reasons (including avoiding unnecessary paperwork) the current Botanic Garden does not sell medicines, but it does play a small role in the production of one. The yew tree Bobart planted in 1645 to look impressive has grown to play a vital part in the production of a drug called paclitaxel. When the Garden’s yew trees are clipped, the leaves are sent off to the manufacturers as the breast cancer medicine is derived from a chemical they contain.

The story of the yew tree and the anti-cancer drug illustrates one aspect of the current Garden that would hardly have crossed Jacob Bobart’s mind: conservation. When Bobart had that yew tree planted he did not know that it would be saving lives three and a half centuries later – he only needed it to look good. Similarly, one of the main arguments in favour of conservation is that it is just common sense to save as much as possible – how can we know what will be useful in the years to come? One species that the Botanic Garden played a starring role in saving is hell’s spurge, Euphorbia stygiana, which can be seen on the other side of the 1648 border’s wall. It grows wild in just ten areas and was classed as ‘endangered’ before the Garden’s intervention, but it is now widely cultivated and out of trouble. Likewise, the Harcourt Arboretum – added to the Garden in the 1960s – has recently undergone a project to restore an area of surrounding arable land. In just three years an intensively farmed field has been transformed into a traditional English wildflower meadow: this is extremely important, as conservation is as much about saving habitats as individual species.

In all these things, the Botanic Garden’s roles are complemented by the large collections of dried specimens that is currently held in the Department of Plant Sciences – the herbaria. They had previously been kept at the Garden, which suited the man one of them is now named after, Professor Charles Daubeny, perfectly. In a speech in 1853 when the herbaria and Garden were united, he said that “a collection of living and of dried plants should always go together,” and this remains the case even though there is now more physical distance between the two. Indeed, some of the very earliest collections are from Bobart the Elder himself, and along with his son’s ‘Dried Garden’ (Hortus Siccus) they give an accurate picture of what the Garden contained in its early days. The herbarium specimens are used in identifying plants, and are also very useful in tracking the changes in the way species have been named, as the sheets have been repeatedly re-labelled through the years in order to keep their names up to date. It can also help scientists track the spread of species introduced from abroad (which are a major threat to biodiversity worldwide) – something particularly relevant to a botanic garden as importing species comes with the territory. Oxford ragwort (Senecio squalidus) escaped from the Botanic Garden in the early eighteenth century having been introduced by Bobart the Younger, and herbarium records show its spread across the country, as well as the emergence of the hybrid species that it created (including York groundsel, found around York railway station).

The Botanic Garden has changed in many ways since Bobart the Elder’s time, but he would doubtless still recognise it. It remains highly devoted to research and education – “the furtherance of learning” – as well as to what Bobart might have called “the glorification of God” in the way it emphasises the beauty and wonder inherent in its plants. He would probably be interested to learn about the ways in which plants are used in modern medicine, and would doubtless be fascinated by the plants from places he would never have even heard of (such as New Zealand, visited by Europeans for the first time just six years before he brought out the 1648 catalogue). He may have been a little jealous that the Garden can now give away its vegetable produce – he spent seven years selling it to get by when the University failed to pay him – and he may well have been aghast at the number of children enjoying the grounds. He would certainly recognise the species in the 1648 collection, though, and he might well be very happy to see his yew tree still standing.