Distribution

Ginkgo is native to China but very few natural populations remain. For hundreds of years gingko has been cultivated and planted as a sacred tree on the grounds of Buddhist monasteries in East Asia, perhaps contributing to the species' survival. It was first cultivated in North America, in the city of Philadelphia, in 1784, and is now planted world-wide as a landscape tree

Living fossil

Ginkgo, like dawn redwood, is a living fossil. It is one of the world's oldest plant species and is the sole remaining survivor of the family Ginkgoaceae, which once contained several genera and species in different parts of the world. Ginkgo has persisted since the time of the dinosaurs. Modern trees are virtually the same as fossil specimens from at least 100 million years ago. This comparison can be seen in the James and Louise Temerty Galleries of the Age of Dinosaurs at the Royal Ontario Museum in Toronto.

Longevity

Ginkgo is capable of living several hundred years. Some specimens in China are thought to be at least 400 years old.

Reproduction and Classification

Ginkgo ovules are fertilized by motile (swimming) sperm, which are released by pollen grains when they germinate. This is a trait that ginkgo shares only with cycads and with the plants that reproduce by means of spores rather than seeds (ferns, mosses, etc.).

Ginkgo does not bear fruit. What appears to be a fruit is actually a seed with a fleshy outer seed coat. True fruits develop from the ovaries of flowers within which the ovules are enclosed. Following pollination, the ovules are fertilized and they develop into seeds, and the ovary develops into the fruit. Depending on the species, a fruit may be dry (e.g. honey locust pod) or fleshy (e.g. tomato). In contrast, ginkgo has no ovary enclosing its ovules. After fertilization, as the ovules develop into seeds, it is the outer part of the seed coat that becomes fleshy. There is no ovary to develop into a fruit.

Seed plants with ovules that are not enclosed by an ovary are known as Gymnosperms (= naked seed), a group that includes ginkgo, cycads, and conifers (whose ovules are borne exposed on the scales of a cone). Seed plants with ovules enclosed in an ovary that develops into a fruit are known as Angiosperms (= seed in a vessel), or flowering plants.

Derivation of names

The name ginkgo is derived from two Japanese words: gin (with a hard 'g'), meaning silver, and kyo, meaning apricot. The species name biloba refers to the leaves, which are often partially divided into two lobes by a notch along the edge. The common name maidenhair-tree refers to the resemblance between ginkgo leaves and those of some maidenhair ferns.

Human use

The seeds are also called ginkgo nuts. The embryo inside the seed case is used in soups or roasted as a snack in various parts of Asia. The wood has no commercial value. Ginkgo extracts have been used for medicinal purposes, perhaps most prominently as a memory aid, although it has not been proven conclusively that it is effective in this regard.

Ginkgo's place in Toronto's urban forest

Because it is tolerant of urban pollution, ginkgo is often planted on streets and in parks. It is prized for its tall, distinguished upright habit and its unusual leaves.

Landscape value and potential for home use

Though slow growing, ginkgo grows to be a very large tree that can dwarf a small property. Male trees are usually preferred because, after the seed has fallen to the ground, the fleshy outer seed coat gives off an odour that has been compared to rancid butter and vomit. It is also very slimy and presents a slipping hazard for pedestrians as it decomposes. Touching the fallen fruit should be avoided, as it may cause skin rashes and the unpleasant smell may linger on the hands long after contact. Selecting a male ginkgo may not be entirely straightforward, as male and female trees appear identical until the trees start to reproduce at around 20 to 50 years old. For this reason, male clones have been developed for planting in urban areas.

Ginkgo prefers deep, sandy, and moderately moist soil, but is adaptable to a range of soil conditions. It grows best in sunny sites.

Pests and diseases: Ginkgo is not known to be susceptible to any pests or diseases.

This tree is available for planting through the City of Toronto's street tree program.

Links to maps at Canadian Tree Tours:

• Toronto Island Park
• Trinity Bellwoods Park
• Queens Park
• High Park

• USDA PlantsProfile (US Department of Agriculture)
• Flora of North America