|Katherine Olivia "Kate" Sessions|
|Born||November 8, 1857
San Francisco, California
|Died||March 24, 1940 (aged 82)
San Diego, California
|Occupation||Horticulturalist, landscape architect|
|Known for||"Mother of Balboa Park"; introduced trees and plants to San Diego|
Katherine Olivia "Kate" Sessions (November 8, 1857 – March 24, 1940) was an American botanist, horticulturalist, and landscape architect closely associated with San Diego, California, and known as the "Mother of Balboa Park."
Sessions was born in San Francisco, California and educated in Oakland. At the age of six, she moved with her family to a farm next to Lake Merritt. She attended the University of California, Berkeley in 1881 with a degree in natural science. While attending a San Francisco business school, at the request of a friend, she moved to San Diego in 1883 to work as an eighth grade teacher and vice principal at Russ School (now San Diego High School). She worked at the school for over a year before she left due to health problems.
In San Diego, Sessions quickly moved on to her true interest, the cultivation of plants. In 1885, she purchased a nursery; within a few years she was the owner of a flower shop as well as growing fields and nurseries in Coronado, Pacific Beach, and Mission Hills. The Mission Hills Nursery, which she founded in 1910 and sold to her employees the Antonicelli brothers in 1926, is still in operation.
In 1892 Sessions struck a deal with the City of San Diego to lease 30 acres (120,000 m2) of land in Balboa Park (then called City Park) as her growing fields. In return, she agreed to plant 100 trees a year in the mostly barren park, as well as 300 trees a year in other parts of San Diego. This arrangement left the park with an array of cypress, pine, oak, pepper trees and eucalyptus grown in her gardens from seeds imported from around the world; virtually all of the older trees still seen in the park were planted by her. Among many other plant introductions, she is credited with importing and popularizing the jacaranda, now very familiar in the city. She also collected, propagated, and introduced many California native plants to the horticulture trade and into gardens. In 1900, she took a trip to Baja California to find a palm tree not native in San Diego to be planted at the park. She would also later take a seven-month trip through Europe where she collected multiple plant varieties that she eventually helped plant in the park.
Together with Alfred D. Robinson she co-founded the San Diego Floral Association in 1907; it is the oldest garden club in Southern California. The garden club was influential in teaching San Diegans how to grow ornamental and edible plants, at a time when most San Diego landscaping consisted of dirt and sagebrush.
Sessions worked with architect Hazel Wood Waterman on the garden design for a group of houses built by San Diego socialite Alice Lee near Balboa Park.
Her work with plant introduction, as well as her extensive writing on the subject, won her international recognition. At the California Pacific International Exposition on September 22, 1935, the day was dedicated to Sessions, where she was named the "Mother of Balboa Park". In 1939 she became the first woman to receive the prestigious Frank N. Meyer medal of the American Genetic Association.
In the San Diego area, the Kate Sessions Elementary school in Pacific Beach bears her name, as does Kate O. Sessions Memorial Park on Mount Soledad, located less than a mile from the school and constructed only a few years later.
A bronze statue of Sessions, dedicated in 1998, is situated in a prominent location in Balboa Park, in the southwest corner of Sefton Plaza, near the Sixth Avenue entrance to the park. It is the only full sculpture in San Diego of a real (non-fictional) woman. 
In popular culture
A 2013 children's picture book, The Tree Lady: The True Story of How One Tree-Loving Woman Changed a City Forever, tells the story of Kate's life, education, and contribution to San Diego civic life.
- Sessions biography (San Diego Historical Society)
- Christman (1985), p. 16
- Showley, p. 73
- Christman (1985), p. 18
- Pourade (1965), p. 32
- Pioneer Park history
- "Our History". San Diego Floral Association. Retrieved 1 February 2013.
- Christman (1985), p. 88
- Christman (1985), p. 20
- "Kate Olivia Sessions". Hillquest, an Urban Guide to 92103. Hillquest, Inc. Retrieved 5 December 2012.
- "The Tree Lady". Beach Lane Books. Retrieved 18 March 2015.
- Christman, Florence (1985). The Romance of Balboa Park (4th ed.). San Diego: San Diego Historical Society. ISBN 0-918740-03-7.
- Pourade, Richard F. (1965). Gold in the Sun (1st ed.). San Diego: The Union-Tribune Publishing Company. ISBN 0-913938-04-1.
- MacPhail, Elizabeth C. (1976). Kate Sessions : pioneer horticulturist. San Diego Historical Society.
- Showley, Robert M. (2000). San Diego: Perfecting Paradise. Heritage Media Corp. ISBN 1-886483-24-8.