We start our stroll in the arboretum, a collection of trees inaugurated in the latter eighteenth century by the Scientific Director Giovanni Marsili. “There was no public garden,” he wrote in a paper. “There were hardly any of the noblest, most widespread members of the botanical kingdom, namely trees. Neither local nor foreign. Very few were to be seen inside the enclosed garden and they were of the more mundane, uninteresting type, occupying space rather than being decorative.” Marsili therefore decided to create a “grove”, as he called it, in an area previously set aside for the Scientific Director’s private use, outside the Hortus Cinctus.

This was outside the oldest part of the garden. Trees need room to grow!

Here you can see the second oldest tree in the garden: the great Oriental plane tree. It was planted in 1680 and is a rarity for two reasons.

Observe it carefully. You may have noticed that it’s a hollow tree. This is an incredible scar, probably caused by lightning. But our plane tree is still here: it survives with its external tissue, which carries lymph, and does without the inner tissue, whose only function is to provide stability and resistance.

To understand the second reason that makes it rare, you should know that plane trees in our cities are hybrids, a cross between the Oriental plane tree also known as the Mediterranean sycamore, and the American sycamore, from North America. How did they meet? Clearly, there’s a human finger in the pie!

This majestic tree in front of you, with its dense foliage, is an Oriental plane tree. In Mediterranean countries it was planted in the centre of towns and its shade offered a place for socializing, maybe even for some philosophical debate, a cultural salon in other words. It was a firm favourite in the gardens of ancient Persia. Northern countries also wanted it, but their climate was too harsh for the Mediterranean sycamore. In 1670, American plane trees were introduced to England as they were more resistant to cold. It was love at first sight! The two species crossbred, producing a fertile hybrid known as the London plane, which turned out to be stronger than its progenitors and is therefore the version we usually meet.

Before going on, listen to this quote from the early twentieth-century American naturalist, Enos Mills, the founding father of Rocky Mountain National Park:

“Trees, like people, struggle for existence, and an aged tree, like an aged person, has not only a striking appearance, but an interesting biography.”