Cyrus the Great of Persia, a famed conqueror from which the recently defeated leader of Team Galactic had taken his name, is said to have kept a supply of Turtwig with remarkably strong shells. He demanded tribute in soil and water from every province – not particularly valuable goods, and therefore thought of as symbolic – as a way to let his Turtwig grow big and strong. His collection was kept with him at all times by the throne as symbol of the size and wealth of his empire. Whenever a province remained loyal long enough that its Turtwig evolved, it would be given to that province's governor – partially as a reward, for Grotle and Torterra conferred immense prestige, but also to quash rebellions and maintain public order.
Turtwig grow slightly differently depending on the composition of the water and soil, most notably in the shapes of their leaves and what shades of green color their bodies. Yet this very diversity which made Cyrus' menagerie possible would ultimately dwindle the numbers of Turtwig to extinction. Human activity, such as waste treatment, farming, and irrigation (and in more recent eras, industrial pollutants as well) has led to soils slightly different in composition from those found in prehistoric times. Although in most plants and grass pokemon, these differences are too modest to be noticed, they have had a catastrophic impact on the wild Turtwig population, which is believed to have gone extinct in many regions including Sinnoh.
A sufficient number of Sinnoh Turtwig have remained in the local pokemon professor's research laboratory to provide a viable breeding population, and digs in the Underground have found soils apparently identical to those of ancient Sinnoh. As of this writing, it appears the Sinnoh Turtwig will survive for generations of trainers to come.