Jensen was born in Denmark and moved to America at the age of 24 and lived in Chicago. In 1900 he became superintendent of Humbolt Park but was sacked and founded a private practice. He is best known for his pioneer work in the use native plants in planting design, an approach which later became known as 'ecological planting'. He described it as a 'prarie style', parallel with the prarie style of Frank Lloyd Wright. Most of his work was on private garden estates and little of it has survived. In 1939 he published a book of his writings, named Siftings.
Gardens designed by Jensen, Jens