Karl Gustaf Johannes, or Gösta, who grew up in a wealthy family, worked in the field already as a child. He decided to pursue agriculture as his vocation. Majoring in botany, Grotenfelt graduated from the Imperial Alexander University in 1877 and then supplemented his studies at the Royal Veterinary and Agricultural University in Copenhagen.
After returning to Finland, Grotenfelt took care of his home manor and its dairy school with his brother. He introduced co-operative dairy operations in Finland and served as a dairy school inspector. In 1891, Grotenfelt was appointed director of the Mustiala Agricultural and Dairy Institute. Mustiala was the highest educational institution specialising in agriculture in Finland before teaching was transferred to the University of Helsinki. Later, Grotenfelt became professor of agriculture and the director of the crop cultivation department of the state pilot plant for agricultural economics.
In his writings, Grotenfelt discussed many important topics, such as dairy farming and bacteriology, arable farming as well as agricultural machinery and tools. He established an agricultural museum in Mustiala for which he personally collected most of the objects on display. Today, they are part of the collections of Helsinki University Museum Flame and the Finnish Museum of Agriculture Sarka.