Introduction

 

Ginkgo, commonly called the Maidenhair Tree, has been in existence for around 200 million years (Ginkgo yimaensis (right), in fossil remains, has been accurately dated to 170 million years ago). The current form, Ginkgo biloba, evolved around 25 million years ago, whereupon the leaves became less divided, giving rise to the well known bilobed characteristic

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But sadly you are more likely to see the 'modern form' Ginkgo biloba cultivated in a garden rather than in the wild, where only a few isolated pockets still grow naturally in China. However, even those have become endangered from habitat loss, pressure on land and resources.

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In eastern China there are some impressive ancient specimens, the oldest of which is The Grand Ginkgo of Li Jiawen (right), which is an incredible 35m tall with a 4.5m diameter. It is around 4,000 years old. There are other notable trees, such as, in the grounds of the Xin Cun Temple, which is a 2,000 year old male tree which had grafted to it a female tree over 1,000 years ago.

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The plant has a history of being used in traditional Chinese medicine. The seeds are used to cure a range of digestive disorders and respiratory problems such as asthma. The leaves can be used to make herbal tea which is said to improve the circulation, memory and may offer some hope in treating Alzheimer's Disease but regrettably early trials have not been conclusive. It should be noted that the leaves were not used as a medicine until 1970 when they were introduced as a 'medicine' by a homeopathic company in Germany.

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In the United Kingdom the oldest and best known example of Ginkgo biloba is 'The Old Lion' planted at Kew Gardens in 1762 (right). This is an impressive specimen tree.

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Description of Ginkgo biloba

 

Overview: Trees reach up to 40m in height and older individuals tend to have a more spreading appearance with irregular branches. The deeply fissured brown bark may appear cork-like in older individuals.

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Leaves: The characteristic greenish-yellow leaves are fan-shaped and composed of two or more distinct lobes; the Latin species name biloba refers to this fact. The common name of maidenhair tree pertains to the similarity of the leaves to those of maidenhair ferns (Adiantum species). In autumn, the leaves of Ginkgo biloba turn a beautiful golden hue before falling to the ground.

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Seeds: It takes 20-35 years for maidenhair trees to reach maturity and start bearing seeds. Male and female trees are separate; male trees have pollen-producing catkins while female trees, once fertilised, bear rounded, yellowish seeds with a fleshy outer coat (resembling a plum in appearance). These fall to the ground in the autumn and as the seed coat decays it exudes a rancid butter-like smell.

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In mid to late May the male trees shed their pollen. It travels in the wind to a receptor (a drop) on the end of the female cones. The pollen is then transferred into the ovule. However, fertilisation (the fusing of the male and female gametes) does not occur until October or November, just as the fruit falls from the female trees. At that moment the male sperm swims and fuses.

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Male flowers, female flowers, pollen receptors and fruit.

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The ripe fruit smells like rotten meat or perhaps rancid butter, which is caused by the presence of butyric acid. This is why most trees planted in public spaces and streets are male. However, in Asia the cooked fruits are eaten as a hangover remedy! It is worth remembering that they are toxic, therefore only small numbers (less that 10) should be consumed.

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One of the finest attributes of Ginkgo biloba is the stunning autumn colour which is produced just before the leaves drop from the trees.

 

Some cultivars are grown because of their ability to reliably produce good autumn colour, e.g. Ginkgo biloba 'Autumn Gold'. Opposite is an example of outstanding autumn colour. People enjoying the autumn foliage under the in Showa Kinen - Koen National Park, Japan.

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