​Ginkgo (Ginkgo biloba) trees also known as Maidenhair trees are slow-growing, relatively pest-free, wind-pollinated trees that can be found in all fifty of the contiguous United States. The only tree species within division Ginkgophyta to escape extinction, Ginkgo biloba is known as an ancient tree with prehistoric fossils dating back 270 million years found on every continent except Antarctica and Australia.

Ginkgo grow best in full sunlight and can reach heights greater than 35 m (115 ft). Ginkgo trees are valuable street trees because of their low susceptibility to smoke, drought, or low temperatures. These trees grow slowly and perform relatively well in most soil types provided they are well-drained. The leaves turn a vibrant​ yellow during autumn but drop soon after its brilliant fall color is observed.

Unfortunately, in late autumn, the dirty secret that female ginkgo trees hide is revealed. The “fruit” produced by female ginkgo trees is foul smelling (has been compared to rancid butter or animal excrement) and is cast in the fall following the first frost. Though immature when cast, the embryos within the fruit continue to mature on the ground for up to two months afterwards. This means that anyone unfortunate enough to step on the fruit during that time is exposed to its pungent odor.

Extreme caution should be used when selecting ginkgo trees for landscape ornamentals or for street trees since there is no way to discern a male from a female at the seedling stage. Several “Boys Only” cultivars have been developed such as ‘Autumn Gold’ or ‘Lakeview’ to ensure that you do not end up with a stinky yard or street when the trees begin to fruit. While the scent of the seed coat may be undesirable, the seed kernel is highly valued in Eastern Asia as a food product. In the United States, herbal extracts composed of ginkgo leaves are believed to improve short-term memory and concentration.

On the campus of Purdue University several ginkgo trees can be found although unfortunately for students the vast majority of these are female and the scent of crushed seed pods often follows many students to class on the bottoms of their shoes. A word of warning, the ginkgo trees planted near Pfendler Hall, Forestry, and the Cordova Center are all females. Watch your step this winter and this is the one rare example of when boys ARE better than girls.

Resources:
Stinky Ginkgo Fruit – Purdue Plant & Pest Diagnostic Laboratory
Ginkgo biloba​ – Purdue Arboretum Explorer
Ginkgo – Encyclopedia.com
Ginkgo biloba L. – USDA Forest Service

Shaneka Lawson, Plant Physiologist & Adjunct Assistant Professor
Purdue University Department of Natural Resources