At age eighteen he was diagnosed with tuberculosis and was forced to stay in bed and be overfed for a year, the only cure known at the time.
After being pronounced well, he was urged to leave the damp climate, so he followed the lead of his two elder siblings and their spouses, moving to the Western part of the United States to settle in Colorado.
Pesman and DeBoer also planned the South Denver subdivision Bonnie Brae which incorporated the used of curved streets for the first time.
Situated on a hillside on the shore of West Denver Sloan's Lake and oriented toward a mountain view, the landscape complimented the beautiful building.
After his contract with the state was completed, he designed the Memorial Park at Crown Hill Cemetery, with various themes, including Greek columns, chimes, a fountain, and one of the earliest sprinkler systems.
Other projects were Las Casitas, a low-cost housing area and the Cherry Creek Apartments on Downing Street.
Many private residences benefited from his expertise including the Joshel House, for which he designed a since-partially implemented landscape plan.
He helped to found the Denver Botanic Gardens and contributed many articles to their publication, the Green Thumb; some were published posthumously.
Pesman was considered important in the development of Colorado in the 20th Century, being one of the 149 professionals whose biographies appear in "Shaping the American Landscape".
In 1958, at the fifteenth International Horticultural Conference in Nice, France, he presented a paper and gave out packets of Colorado's native plant, the columbine, to attendees.
In the obituary, he thanked all of his friends and relatives, writing, “This last chapter of my life should be like the final act of a good play.
Will you forget that this is a farewell and keep your memories fresh with all the wonderful times we have had together?” In January 1963, the Colorado Nurseryman's Association chose him as "Man of the Year", posthumously.