Strange fruit: an oak apple gall. Photograph: Paul Evans
Country diary: Today was once a public holiday, thanks to these oak 'apples'
The Marches, Shropshire: You never know what kind of parasites you might find lurking in an old tree
"Oak apple day, the 29th of May," is a rhyming reminder of the public holiday ordered by Charles II to celebrate the restoration of the monarchy in 1660. After his escape from parliamentarians by hiding in an oak tree at Boscobel in Shropshire, it is no great leap of imagination to associate a hidden king with oak apples: parasitic galls are strange, uncanny fruit that encourage satire at least.
A month ago, the oak galls on this ancient tree were as shiny as cherries. Today they are bigger, browner and mottled, like weird little apples. They were formed when an agamic, wingless, female oak apple gall wasp, Biorhiza pallida, burrowed out from a gall in the oak's roots, climbed the tree and injected a cluster of eggs and a drop of venom into a leaf bud. The hatched grubs then produced substances that caused a tumour-like effect on the oak cells, forming the apple, inside which the larvae fed in their chambers.
The exit wounds suggest some larvae have already metamorphosed into adults and left. Shiny-brown, winged males flew off searching for females; the females climbed down to the soil to find a rootlet in which to lay a single egg gall for next year.
Rich Habitat Within the Gall
The Biorhiza larvae may not be the only inhabitants of the oak apple; it is a rich habitat. Other species of inquiline gall wasps live commensurately there, including some of the many species of hyperparasitic wasps whose larvae feed on them; there are also specialised communities of fungi and microbes living in the apple. Did people in the 1600s think of these freaky fruits as magical objects?
Meanwhile, the north wind has dropped. The showers have stopped and the sun has come out. The air is spicy with may blossom. Lambs and ewes lie on warm grass, dozing. A thrush sings from nearby trees and a blackbird perches on an oak root buttress. To stand in this pastoral scene is to time-travel. Under an oak older than Charles II, its ancient shade reads of a point in time where natural magic meets natural history, written in an ink made from oak apples.
With oak apple day no longer a public holiday, perhaps, 366 years later, we make it a celebration of the restoration of nature. Under the Changing Skies: The Best of the Guardian's Country Diary, 2018-2024, is available now at guardianbookshop.com
