Pekka Jyränkö, born in Helsinki, was trained at the horticultural institute at Lepaa. He joined the Parks Department in 1959 and served as City Gardener from 1975 until his death in 1995. Unlike his predecessors, Jyränkö did not design any parks himself; rather, he developed the city's parks in many ways at the same time.
Jyränkö had a wide-ranging interest in plants and their uses. He was particularly fond of trees, and during his period in the post a large amount of street trees were planted, the production of large Finnish trees was promoted and Tree Radar was developed. Jyränkö also advocated plant surveys and breeding, such as the KESKAS research of hardy plants, a survey of Helsinki's poplar trees and exploiting the plant experiments undertaken by his predecessor, Bengt Schalin.
Pekka Jyränkö gave lectures, improved contacts with residents, and played an active part in horticultural organisations. Under his leadership, the Helsinki Parks Department participated successfully in international garden exhibitions. In 1990, the honorary title of Gardening Counsellor was bestowed upon Jyränkö. He was the widely recognised head of the Parks Department, the City Gardener with strong personality. The final years of his successful career were overshadowed by the future of the Parks Department and the status of urban green areas in general.