Posted On: September 24, 2015
Meet the Trees: Ginkgo Biloba
Ginkgo biloba is one of the most historically interesting tree species in the Park. The ginkgo is a living fossil, with fossils recognizably related to modern ginkgo from the Permian period, dating back 270 million years. The closest living relatives of the Ginkgo are the cycads, which share with the extant G. biloba the characteristic of motile sperm.
Fossils attributable to the genus Ginkgo first appeared in the Early Jurassic, and the genus diversified and spread throughout the northern most super continent about 200 million years ago. It declined in diversity as the Cretaceous progressed with the extinction many species leaving only Ginkgo cranei and Ginkgo adiantoides, in the Northern Hemisphere.
About 1.8 million years ago, Ginkgo fossils disappeared from the fossil record everywhere except in a small area of central China, where the modern species survived. For centuries, it was thought to be extinct in the wild, but is now known to grow in at least two small areas in Zhejiang province in eastern China’s Tianmushan Reserve. Recent studies indicate high genetic uniformity among Ginkgo trees from these areas, arguing against a natural origin of these populations and suggesting the ginkgo trees in these areas may have been planted and preserved by Chinese monks over a period of about 1,000 years here fossil species of Ginkgo can be reliably distinguished.
Ginkgo trees were highly prized for their medicinal, edible, and ornamental characteristics. The leaves are unique among seed plants, being fan-shaped with veins radiating out into the leaf blade. Ginkgos are often referred to as the “maidenhair tree” is because the leaves resemble some of the pinnae of the maidenhair fern, Adiantum capillus-veneris. Ginkgos are prized for their autumn foliage, which is a deep yellow.
Ginkgo reproduction is incredibly unique to plants. Ginkgos are dioecious, with separate sexes, some trees being female and others being male. Male plants produce small pollen cones with sporophylls, each bearing two microsporangia spirally arranged around a central axis. Female plants do not produce cones. Two ovules are formed at the end of a stalk, and after pollination, one or both develop into seeds. The seed is attractive in appearance, but contains butyric acid and smells like rancid cheese.
While the seeds are a popular food source in Chinese cultures, they are not valued ornamentally because of their fragrance. Male trees are preferred in the landscape because they do not produce seeds. A combination of resistance to disease, insect-resistant wood and the ability to form aerial roots in some climates make ginkgos long-lived, with some specimens claimed to be more than 2,500 years old.
17 Ginkgo trees exist in Madison Square Park. The most beautiful one can be seen at the center of the oval lawn. Ginkgos are majestic trees when grown in full sun. When grown in shade, Ginkgos can take on interesting shapes. Our specimens on 23rd street are a perfect example of the interesting forms these trees can take.