Ginkgos Are Living Fossils

Ginkgos Are Living Fossils

Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist

Did you know early in the last century petrified Ginkgo biloba (pronounced GINGK-go bi-LO-ba) logs were uncovered near the Columbia River in Central Washington?  It's believed that ginkgo trees once formed large forests in this area ... over 30 million years ago.  They were preserved by sediments and lava flows that occurred in the Central Washington area.

Jack Hampton, Washington State University Master Gardener, was a nut and fruit enthusiast who passed away in 1999.  He was a local expert on nuts.  Hampton said that, "Most people don't recognize ginkgo trees as nut trees, but they are actually the world's oldest cultivated nut.  At present Ginkgo trees probably don't exist anywhere as wild trees, but 150 million years ago, during the Mesozoic era, they enjoyed widespread distribution throughout the northern temperate zone.  At this time there were dinosaurs, marine reptiles, pterodactyls, ammonites, ferns, and gymnosperms (plants with naked seeds not enclosed in a fruit) inhabiting the earth. Mammals, birds, and angiosperms were just beginning to appear. Angiosperms are basically flowering plants (with seeds enclosed in a fruit.)  The ginkgo is the only non-extinct gymnosperm that has seeds that are not produced in a cone.  They are a living fossil!"

There have been many fossils of the characteristic ginkgo leaves found from the Jurassic and Triassic Periods (135-210 million years ago) when dinosaurs roamed the earth.  The ginkgo forests in North America were wiped out long ago by catastrophic geological and environmental activities, such as floods and the ice age.  So how come do we still have living ginkgo tree around today?   The Ginkgo survived the Ice age because the sheets of ice didn't reach parts of southeast China.  Ginkgoes were able to survive the ancient forces of nature and were later cultivated in temple gardens for centuries by Chinese monks.   All the living ginkgoes that are around today are descendants of these Chinese ginkgoes. 

It's easy to identify a ginkgo tree with its unique, fan shaped leaves.  They haven't changed much in 200 million years!  Ginkgo trees are either male or female.  Hampton notes that the "female tree bears a plum-sized fruit that has a disagreeable odor when ripe.  The pulp may also cause an allergic dermatitis and contact with the skin should be avoided." The odor of the fruit has been compared to rancid butter and dog manure, but I think it's much worse.  Watch out if you step on one... they are odoriferous little land mines.    Hampton wonders what types of animals fed on these to spread them throughout the world in prehistoric times...  obviously ones without a refined sense of smell!

Most people try to avoid planting female ginkgo trees so they can avoid getting these attractive yet stinky fruit.  Unfortunately, sometimes they end up with female trees even though they were supposed to be the non-bearing male trees.  Oops!  You will find a few female Ginkgo trees growing in this area and if you are the curious sort you might want to know how to harvest the nuts.  Hampton offers these tips on harvesting Ginkgo nuts, "Gather the ripe fruits using rubber gloves.  Squeeze out the seeds in a bucket of water, wash them thoroughly, and then dry them.  The result will look like a large unsplit pistachio nut.  They are not ready to eat at this point.  To prepare them for eating, first crack them with a pair of pliers.  Then boil them for about ten minutes.  The inner skin (called a pellicle) will fall off leaving a light yellow kernel.   It's this kernel which you eat.  It tastes something like sweet corn.  You may keep these nuts in your refrigerator in plastic bags for a short time, but they are highly perishable."  Hampton noted that the "Chinese have long eaten these white nuts on special occasions, such as weddings and holidays."    He also cautioned that those new to eating Ginkgo nuts observe caution with this new food.  Eat it only in small quantities until you have determined that you have no allergies to the nuts.

If the opportunity to have a living fossil in your own yard intrigues you, you'll be happy to know that you can grow a ginkgo tree quite easily in this area.  Hampton pointed out that ginkgo trees are hardy, adaptable trees that grow in a wide variety of soils and climates.  They are tolerant of drought and urban air pollution. 

As a young tree, a ginkgo has an upright, irregular pyramidal form, and become broader, and more symmetrical with age.  It reaches a height of 50 to 80 feet at maturity. It grows relatively slowly.  Ginkgo trees are remarkably free of pests and disease problems and quite reliably develop wonderful yellow-gold fall color.  They do best if planted in a well-drained, sunny location.  It does take them a while to recuperate after transplanting.

One special thing to remember when you purchase your tree is that you want a male tree.  Remember the ginkgo is dioecious, meaning there are separate sex trees.  You'll have to take the nurseryman's word for it though... as it takes about twenty years before they start bearing nuts.  There are several selected cultivated varieties that you may want to look for in the nursery.  They are 'Autumn Gold' (a male with a broad, spreading form), 'Pendula' (with branches more or less pendulous), 'Shangri-La' (fast growing with compact form), and 'Princeton Sentry' (an upright form, male.)