Sexy persimmon

A few years ago Jane Edmudson on the ABC’s Gardening Australia described some persimmons as suitable for eating like an apple. Others, she said, are almost inedible due to their astringency. There are some 1000 cultivars so you have plenty to choose from.

As you’d expect if you read my recent post about how the Globe Artichoke can change our sensation of sweetness, it’s the phenolics in persimmons that pucker your mouth. In this case, mostly tannins.

Apart from causing mouth puckering, the tannins in the fruit of Diospyros kaki, the persimmon, can be used for waterproofing, food preservation and dyeing. The fruit and leaves also have some potential medicinal uses, currently under investigation: I gather you might already find persimmon extract in 'athlete's foot socks and soap'.

As I discovered in my local park, where a single persimmon tree has been placed among a collection of other edible-fruit trees, the flowers are either male or female. Although on the same plant in this specimen, they can sometimes male on one plant and female on another.

The females (above) have the green, leathery, almost-Elizabethan collar that ends up ornamenting the fruit (see top of post). The male flowers (below) are pretty insignificant in comparison, and look like they might just be spent blooms.

Varieties that produce fruit without seed don’t need to be pollinated, but fully loaded fruits need male flowers in the vicinity. In US orchards farmers grow trees in a ratio of eight female to one male, although I did read that trees can change their sexual orientation from year to year, which if true would make this tricky!

So I tracked down some authoritative advice from the University of California in Davis (USA) on, as they put it, 'what makes a persimmon a boy or a girl'...

One in 20 plant species have flowers on a single sex. It's a great way to mix up genes during pollination, making sure flowers don't pollinate themselves or, if the flowers are on separate plants, don't pollinate with flowers on the same plant. There are other ways to stop this happening, but dioecy, as it's called when single-sexed flowers are on separate plants, is a good way.

The scientists at University of California say persimon plants are either male or female, which makes my parkland plant a little odd. My plant would be described as monoecious meaning that while it has single-sex flowers (either male or female) these are born on the same plant. A dioecious plants has only male, or only female, flowers.

This I remember from Botany 101, or whatever we called it, although the terminology gets a little confusing when transferred to algae, where I drifted later in my studies...

So this, my parkland plant, is monoecious and my American university colleagues say persimons are dioecious? I needed to read more closely... These guys were working on a different species of persimmon, Diospyros lotus, sometimes called the Date Persimmon or Lilac Persimmon. It has smaller fruits and, it seems, a slightly different sex life.

The researchers were looking for the gene that coded for maleness or femaleness. That is, what makes it a boy or a girl persimmon? They found a gene system they call OGI-MeGI: ogi is Japanese for male tree, megi for a female tree. Their next task is to see if this kind of system is universal in all plants, and to see if they can introduce dioecy into the 95% of plants that don't have unisexual flowers on separate plants to help with breeding and plant health.

Meanwhile, back in the park, I'm going to have to track this plant to see if it keeps producing flowers of both sex (monoecious) or switches to only one sex (dioecious). I'll get back to you in a few years, perhaps.

Images: The flowers and young tree are from the park near where I live, photographed in December 2014, and the fruit from a Grow Organic website.