The ginkgo is an interesting tree. It has no known living relatives and is frequently called a "living fossil." Unique in its classification and growth habits, ginkgo trees are rarely found in the wild. Commonly cultivated for ornamental and commercial purposes, ginkgo trees provide a unique experience to gardeners looking to add one to their property.
Ginkgo, classified scientifically as Ginkgo biloba, is the only known living plant within the scientific division Ginkgophyta. While several similar plants existed during the Mesozoic era, they have long since become extinct, which is why the term "living fossil" is so often applied to this tree. The ginkgo tree is also sometimes referred to as the maidenhair tree, due to the similar appearance it bears to the maidenhair fern.
Ginkgo trees reach heights of 65 to 115 feet, with exceptionally large trees growing upwards of 150 feet. The silhouette of the ginkgo tree is roughly triangular, though younger trees grow fairly straight and do not possess the same angular crown as older trees. The leaves of a ginkgo tree are fan shaped, with veins spreading throughout the leaf from the central petiole, or stem. Average leaves grow between 2 and 6 inches in length. Leaves turn a pale yellow color in the autumn, and drop soon after turning.
Hardy to USDA zones 3 through 8, the ginkgo tree prefers full to partial sun, though it is generally considered highly shade intolerant. Moderate watering is recommended, and well-drained soil of a moderate alkalinity (between 5 and 5.5 on the pH scale) is required. Ginkgo trees have no known pests or illnesses associated with their cultivation.
Ginkgo trees are used for shade in urban areas, as they are tolerant of pollution and the rigors of city life. Kept small, they are also used in the art of bonsai. The fruits of ginkgo seeds, referred to as ginkgo nuts, are considered a delicacy in Asian cuisine. The leaves have been used medicinally for centuries to treat memory loss and dementia with mixed results in clinical trials.
Ginkgo leaves contain the oil urishiol, the same toxin that causes allergic reactions from poison ivy and poison oak. While the tree contains much less of the irritant, ingestion of the leaves or teas, pills and extracts created from the leaves may cause adverse reactions in those who have a urishiol sensitivity. Those who are extremely allergic may not want to handle the leaves or prune the tree with their bare hands.