Posted by: Hourglass PJ27 MAY 2010
Today, 29 May, is Oak Apple Day, also known as Royal Oak Day. It is a former public holiday celebrated in England to commemorate the restoration of the English monarchy 350 years ago on 29 May 1660 following the English civil war.
Samuel Pepys wrote in his diary on 1 June 1660: “Parliament had ordered the 29th of May, the King’s [Charles II’s] birthday, to be forever kept as a day of thanksgiving for our redemption from tyranny and the King’s return to his Government, he returning to London that day.”
Oak Apple Day was a time for dancing and parties. To show their support for the monarchy, people wore sprigs of oak leaves or an oak sprig with an oak apple on it. Although the public holiday was abolished in 1859, the day is still celebrated in parts of England.
But what are oak apples? They are not apples at all but deformed oak leaves, produced by the action of certain species of gall wasps such as Biorhiza pallida. According to Samantha Bates, of James Maddison University, Harrisonburg, US, in May a wingless gall wasp inserts an egg into the base of a vegetative bud. This activates the oak into forming a protective structure, the gall, around the egg.
The gall matures in June and July and is usually 3–5cm in diameter. The outside is green and darkens with age while the inside consists of a juicy, white, spongy substance with a small, hard centre where the maturing wasp is found.
By late July, the next generation of wasps emerges. Unlike the first generation, they are fully winged and of both sexes. They exit the gall through small holes, after which the gall shrinks and blackens.
The emerging wasps mate, and the females burrow into the soil and insert their eggs into the oak tree’s roots, where spherical brown root galls form. These mature in about 16 months and the third generation emerges. Like the first generation, these are wingless females, which climb the tree’s trunk to lay eggs in the leaf buds. And so the cycle continues.