A begonia was a type of flower found on Earth.
In 1963, the Eighth Doctor bought a begonia from Fitz Kreiner. (PROSE: The Taint)
In 1964, Rachel Jensen took up raising begonias after retiring. (TV: Remembrance of the Daleks, PROSE: Who Killed Kennedy)
In 2018, a begonia from Graham O'Brien's house in Sheffield joined forces with the renegade Gardener Nightshade helping him track the Doctor's TARDIS. (PROSE: The Secret in Vault 13)
Begonias went extinct before the 26th century, but seeds were preserved at a secret base on the Moon. Bernice Summerfield found the base and took the seeds. She gave them to Professor Sabron Jones to grow in his gardens on Dellah. (PROSE: The Mary-Sue Extrusion)