Born into the wizarding Buchanan family sometime in the mid-19th century, Flora grew up in a village in the Scottish Borders with ten siblings, including Hamish and Angus (the latter of whom, at least, was younger than her). The Buchanan children had a reputation for being rowdy and large. Flora and her sisters won the village tug-of-war competition every year.
When Flora turned eleven, she received a Hogwarts acceptance letter, and began attending Hogwarts School of Witchcraft and Wizardry. The local Muggle villagers, who were unaware of the Buchanan family's magical heritage, assumed that she had been sent to a corrective facility or mental institution. It is unknown which House she was sorted into whilst she attended Hogwarts.
Flora and her other siblings were especially fond of their brother Angus. Since their father was highly prejudiced against Squibs, Flora and her siblings covered for Angus when, unlike them, he displayed no signs of magical ability. After no Hogwarts acceptance letter arrived for Angus, Flora forged one for him, thus keeping their parents in the dark for a few more weeks.