The Suns of Caresh
Erekan was a planet in Mutter’s Spiral. It was within a few dozen light-years of Earth.
Flowers on Erekan did especially well in the cold. They covered a meandering continent covering glacier which crossed the planet’s equator forty-four times. The Third Doctor visited the planet to help calibrate the TARDIS navigational computer. (The Suns of Caresh)