Ginkgo biloba is a very unusual tree. It is believed to be the only surviving species from a group of trees which had their heyday 200 million years ago. Taxonomically speaking, the ginkgo is about as closely related to the oak as human beings are to reptiles.
The tree itself may not be not much to look at, but its fan-shaped leaves are unique. At this time of year they turn a stunning shade of yellow. After a sharp frost it is not unusual for them to fall en masse, forming a brilliant carpet beneath the tree.
On a recent visit to Sheffield Botanical Gardens I noticed that the fallen leaves of ginkgo have an unusual property. Each leaf is divided by many closely-spaced veins, which radiate out from the leaf stalk. On the underside of the leaf the veins stand out, forming a pattern of fine ridges like a freshly ploughed field. When drops of rain fall on a leaf the ridges cause surface tension to pull the water into a near-perfect sphere.
In bright but oblique autumnal sunshine, each spherical droplet acts as a lens and focuses a tiny spot of light - making it look just like a miniature crystal ball.
I managed to get a picture of this phenomenon but, unfortunately, I didn't have my macro lens with me. Today I went back, properly equipped, to get some close-up shots. Sadly, the results were rather disappointing due to poor light. I think the gardeners must have thought I was crazy, kneeling amongst the fallen leaves with my backside in the air!
Undeterred, I took a handful of leaves home and attempted to re-create the phenomenon under 'studio conditions' (i.e. on the dining table, lit with a torch). The results are not bad, but would be better with stronger illumination.
By the way, there's a blog which is entirely devoted to celebrating ginkgo.