The Maidenhair tree, Ginkgo biloba, is perhaps one of the most iconic trees in cultivation. Often referred to as a living fossil, Ginkgo is one of the oldest seed plant lineages to have survived through to the present day with a fossil record stretching back over 200 million years. The fan shaped leaves are unlike any other tree and makes it instantly recognisable whether as a living tree or fossil remain.
This tree has a long association with mankind. Once its ancestors were widely distributed across both northern and southern hemispheres although global climate change over many millennia has now reduced its natural distribution to just a small grove in south-east China. Regarded as a sacred tree in the East it has long been planted around temples and perhaps some of the oldest and most revered trees can be found in their vicinity. It was from Japan that seed was first introduced to Europe and then North America and it was perhaps the first Asian tree to be widely planted as an ornamental shade tree. Its ability to survive pollution and varied conditions means it is now a favoured street tree in the US, southern Europe and Asia.
There are several trees planted around the Botanic Garden, a small specimen in the New Pinetum and several in the autumn colour area where their clear butter yellow foliage is a star attraction in October. Perhaps the best specimen is located at the western end of the glasshouses where it grows at the back of the courtyard, partly screening the old Curator's house beyond. This tree recently revealed a long held secret as it proved to be a rare female tree shown by the production of the pale yellow fruits over the last two years. They are known as Japanese or silver apricots and the hard nuts inside the fruits are edible. However, the fleshy pulp has a rather rancid smell so most nurseries select only male clones for sale.
Perhaps the most interesting specimen is one trained as an espalier against the northern side of Cory Lodge. The short spur like branches lends themselves well to training in this way. However, this specimen pails in size compared to the large espaliers now over a hundred years old trained against the southern side of Plant Sciences on the Downing site. The two plants originally from Montpellier Botanic Garden in France are a male and female although the annual pruning needed prevents fruit production. It is these fine specimens that inspired the logo for Plant Sciences, a Ginkgo leaf entwined by the double helix of a DNA molecule.
Ginkgo biloba thus seems a natural choice to enhance the entrance to the new Sainsbury Laboratory to be opened later this year. This autumn a grove of 27 trees will be planted across the entrance plaza to embed the building into the surrounding landscape and to represent one of the key purposes of the new laboratory to help understand the origins of plant diversity.
Other tree planting around the Laboratory are inspired more by the prospect of future climate change and the likelihood of hotter and drier summers. Taking advantage of the microclimate within the courtyard of the Laboratory will be a grove of olives, Olea europaea. These Mediterranean trees have become a more common site in local gardens and there are now frequent reports of fruit set. Visitors will be able to view any harvest from the new cafe. To provide summer shade trees of a Chinese Lime, Tilia henryana, will be planted along the south side in the seating area for the cafe and pruned as low spreading parasols. This lime has particularly beautiful sculpted leaves with bristle-like tips to the serrated leaf edges. It is rarely planted in the UK as a street tree although is encountered more frequently in the cities of southern Europe. Planting of these trees will take place this autumn into specially designed tree pits designed for use around buildings and in areas of hard landscaping. We can look forward to seeing their progress next year.
Dr Tim Upson, Curator
Friends' News Issue 84, September 2010