Parsons then went to school at Yale University and graduated with a Bachelor's degree in philosophy in 1862, after which he spent several years studying and practicing farming.

When he returned home to the family nursery, it had started supplying Frederick Law Olmsted and Calvert Vaux, two famous designers responsible for the Greensward Plan for New York City's Central Park.

When Vaux became the head landscape architect of the New York City Parks Department, with him came Parsons, who took over the unpaid position of Superintendent of Planting.

Throughout his professional career, Parsons was known for his ability to merge elegant plantings and the extensive knowledge he had gained from his father with the native environment without disrupting the Genius Loci (the spirit of place) of the sites he designed.

He remains a founding father of the modern day landscape architecture institution, and his designs are still visible throughout the United States, primarily in San Diego’s Balboa Park and New York City's Union Square.

Together with oaks they predominated in 80 million hectares of forest from Maine to Florida and west to the Ohio Valley, reaching heights of up to 40 metres (130 ft) and growing two meters around the middle.

Lightweight, rot-resistant, straight-grained and easy to work with, chestnut wood was used to build houses, barns, telegraph poles, railroad ties, furniture and even musical instruments.