Ginkgo biloba

This particular tree is quite large for our area. While we do not know the exact age of the tree, we are confident that it predates the existence of our university under any of its names. It was likely planted intentionally by the Whitney family, who owned the land. As one of the older members of our community, this tree has witnessed many graduation ceremonies to date. The grounds crew at Rowan takes great care to keep it healthy. Such a large tree has an enormous underground root system, so they add mulch from near the base of the trunk all the way to the drip line of the tree. The “drip line” is like the footprint of the canopy of leaves and branches if you were looking down from above.  Mulch, which is the dark organic matter made of aged leaves and ground bark around the base of the tree, helps to reduce competition from other plants and holds in moisture. Importantly, it also prevents things like mowing equipment from getting too close and damaging the tree. 

If you are arriving during late fall or winter, this tree might be naked because it is deciduous, which means that it drops its leaves with the seasons. The leaves turn a vibrant yellow color before they fall. Often this tree is planted in gardens solely for the desirable leaf color in autumn.  The shape of the leaves is unique, usually described as fan-shaped. See if you can touch a leaf, either from the tree or off the ground; they may feel leathery to the touch. Notice that the veins, which transport water and nutrients to and from the leaves, are almost parallel. The leaves can also split in the middle and have two lobes, hence the species name biloba. Leaf and seed extracts from this tree have been used in traditional herbal medicines for centuries, and they continue to be sold as foods and supplements. Trees in China, France, and South Carolina are major producers of Ginkgo leaves – about 8000 tons per year commercially. We have included resources below to help you learn more about the pharmacological and medicinal properties of this species.

Members of this species don’t reach sexual maturity until aged 20-30 years. While many tree species are bisexual, this species is not. It is a dioecious species. This means that male and female structures are located on separate trees. Thus, this particular tree is truly a mother tree – not a father. It will only produce ovules, not pollen. If you take a stroll around Bunce circle, the periphery of University Green, you will find several smaller male Ginkgo trees.

Male trees have pollen-producing cones, and pollen contains motile swimming sperm. Females, like this mother tree, produce ovules that develop into seeds after they are fertilized by sperm. For mature trees, sexual reproduction occurs in the spring (~April) via wind pollination. After fertilization, seeds, which are sometimes called “nuts,” mature on the tree. “Nuts” drop from female trees approximately one month after fertilization, which usually happens between August and September. If you are visiting this tree around that time of year, you may see the yellow nuts beneath the tree. Squirrels can disperse the mature “nuts” that fall, but many animals seem to avoid them. This is probably because mature seeds have a fleshy covering (sarcotesta), which contains butyric acid. This compound is also found in rancid butter, so the “nuts” are described as smelling like vomit when they decompose. Here, the grounds crew often removes them after they drop. Usually, male trees are cultivated to avoid the smell and mess of the fleshy nuts, but pollen from male trees can cause allergies for some people. 

Although it is sexual, this species will never make flowers or fruits. As an ancient lineage, it diverged before the evolution of these structures. It is a member of the group of plants that are described as having “naked seeds” – the gymnosperms. Other members of this group include the cone-producing conifers. I encourage you to keep exploring the trees on Rowan’s campus. You can learn more about conifers, as well as many trees that do make flowers and fruits. We are excited to share our love of these important members of our community with you!

I am Dr. Sara Wright, and these resources are a product of my Plant Diversity course in the Biological Sciences Department. You can read more about me and the Ginkgo tree below.