Tradition dictates that a royal bride's bouquet contains a sprig of myrtle.
The custom dates back to Queen Victoria's time when the monarch's daughter, Princess Victoria, carried it among her bridal flowers in 1858.
The Duchess of Cambridge, the Queen, and Harry's mother, Diana, Princess of Wales, all had myrtle in their wedding bouquets - so it is expected that Meghan Markle will do the same.
The myrtle for royal bridal bouquets comes from the bush grown from the myrtle originally given to Queen Victoria.
It was presented to Victoria in a posy by Prince Albert's grandmother, and the couple brought it back from Germany and planted it at Osborne House, their holiday home on the Isle of Wight, where it has thrived.
The glossy, evergreen shrub is said to bring luck and fidelity.
In another tradition, royal brides poignantly send their bouquet back to Westminster Abbey to be placed on the Grave of the Unknown Warrior.
Kate followed the custom in 2011, as did the Queen, who was Princess Elizabeth when she wed in 1947, and Diana in 1981.
The resting place at the London Abbey holds the remains of a First World War soldier who has come to symbolise the nation's war dead.
The late Queen Mother began the long-standing tradition when her posy was left at the grave in 1923 after her wedding to the Duke of York, later George VI.
She left the flowers in memory of her brother Fergus, killed in 1915 during the global conflict.
Convention dictates that the day following royal weddings the floral tribute is sent to the Abbey after the official wedding pictures of the bride and groom have been taken.
Kate's bridal bouquet, which included sweet William, as well as myrtle, lily of the valley and hyacinth, was placed on a small pillow on the grave.
Diana's flowers consisted of white and gold stephanotis, gardenias, orchids, lily of the valley and yellow Earl Mountbatten roses.
The Queen chose white orchids for her bouquet.
The Unknown Warrior's body was brought from France and buried on Armistice Day, November 11 1920.
It is thought the idea came from the Rev David Railton, who had served as a chaplain on the Western Front.
It is now one of the most visited war graves in the world.