Birching is a corporal punishment with a birch rod, typically applied to the recipient's bare buttocks, although occasionally to the back and/or shoulders.
A birch rod (often shortened to "birch") is a bundle of leafless twigs bound together to form an implement for administering corporal punishment.
Contrary to what the name suggests, a birch rod is not a single rod and is not necessarily made from birch twigs, but can also be made from various other strong and smooth branches of trees or shrubs, such as willow. A hazel rod is particularly painful; a bundle of four or five hazel twigs was used in the 1960s and 1970s on the Isle of Man, the last jurisdiction in Europe to use birching as a judicial penalty.
Another factor in the severity of a birch rod is its size - i.e. its length, weight and number of branches. In some penal institutions, several versions were in use, which were often given names. For example, in Dartmoor Prison the device used to punish male offenders above the age of 16 - weighing some 16 ounces (450 g), and 48 inches (1.2 m) long - was known as the senior birch.
In the 1860s the Royal Navy abandoned the use of the cat o' nine tails on boy seamen. The cat had acquired a nasty reputation because of its use in prisons, and was replaced by the birch, with which the wealthy classes were more familiar, having been chastised with it during their schooling. Around the same time, the civilian courts system followed the Navy's example and switched to birches for the judicial corporal punishment of boys and young men, where previously a whip or cat had been used. In an attempt to standardise the Navy's birches, the Admiralty had specimens called patterned birch (as well as a patterned cane), kept in every major dockyard, as birches had to be procured on land in quantities.
The term judicial birch generally refers to the severe type in use for court-ordered birchings, especially the Manx hazel birch. A 1951 memorandum (possibly confirming earlier practice) ordered all UK male prisons to use only birches (and cats-o'-nine-tails) from a national stock at south London's Wandsworth prison, where they were to be 'thoroughly' tested before being supplied in triplicate to a prison whenever required for use as prison discipline.