Tellus IV

 was a planet of the Gardeners. It was not far from Calufrax Major.

Originally Tellus IV was a hot, barren world. When the Gardeners brought topsoil from their home world to Tellus IV, they transformed the planet into a garden that smelled of freshly mown grass, and had sheep dotting the landscape.

All types of gardens and greenhouses were represented on the planet, including walled gardens, wild gardens, zero-G gardens, hanging gardens and hanging baskets. The glasshouses of Tellus IV were considered architectural achievements.

The Thirteenth Doctor, Graham O'Brien, Ryan Sinclair and Yaz visited the planet, by the invitation of the Gardeners. (PROSE: The Secret in Vault 13)