Q: Why do some ginkgo trees produce fruit and others don’t? We have one in our street that fruits every year in autumn, while a much larger one at my work has never fruited, as far as I know.
Question from T. Bulmer, Auckland
A: There’s a simple reason, ginkgo trees are dioecious plants. Dioecy is Greek for ‘two households’, so with plants dioecious means there are separate male and female plants in a species. With Ginkgo biloba some trees are male and others are female. In cone-like structures, the male tree produces pollen, which is released to drift in the wind. The female tree produces two ovules on the end of a short stalk exposed to the drifting pollen. Once pollinated the ovules develop into seeds around 2cm long surrounded by a fleshy layer, looking a bit like a yellowish cherry or small plum, but when ripe smelling rather disgusting, like vomit.
In short, only female ginkgos produce seeds, so the one at your work is almost certainly a male. If you grow ginkgo seeds, there’s no way of telling the sex of the seedlings, you have to wait for years until the trees reach ‘flowering’ age. If you want to buy a ginkgo tree of known sex you need to buy a grafted plant or one grown from a cutting; grafting wood or cuttings taken from a male tree will always be male, and likewise grafting wood or cuttings from a female tree will always be female. It can be useful to know the sex of a ginkgo tree before buying one as the smell of the fruit can be quite unpleasant, yet on the other hand many people collect the seeds and eat them for their reputed health-giving properties.
Extract of ginkgo leaves is also claimed to have beneficial properties, particularly in mental and cognitive functioning, and is found in some of the many health supplements available these days.
Answer by Andrew Maloy (The Plant Doctor)