Stemless gentian or Gentiana acaulis is one of many other gentian species. Stemless gentian is spring flowering; in bloom, the plants are covered with upward-facing deep blue flowers, 2 to 3 inches across, marked with green or white throats. The shiny leaves, 1 inch long and 1/2 inch wide, spread on underground stems to form thick mats up to 18 inches across. Among the varieties of this gentian is one with white flowers, 'Alba', and a plant with 4-inch flowers, 'Gigantea'. Sometimes the stemless gentian will not bloom, or blooms once and never again, for an unknown reason. The rough gentian has fall-blooming dark blue bell-shaped flowers clustered at the tips of stiff, upright stems. Its leaves are oval, 2 to 3 inches long, with rough edges. Normally this gentian is 12 inches tall and its flowers are 1 to 1 1/4 inches long.
Info taken from Time Life Plant Encyclopedia.

I'm actually not sure which gentian species Ken's image flower is. But my guess in this stemless gentian^^; because it looks the most similar with the one in the anime^^;; Gentian is called 'rindou' in Japanese.