Lomatium observatorium, commonly known as Mt. Hamilton desertparsley and Mount Hamilton lomatium, is a rare species of flowering plant in the carrot family (Apiaceae). The species was first described in 1996 by botanists Lincoln Constance and Barbara Ertter in Madrono. It is endemic to California, where it is known only from the mountains of Santa Clara County, including Mount Hamilton near the Lick Observatory, with possible occurrences in adjacent Stanislaus County. Its habitat includes mountain woodlands on volcanic and metamorphosed sedimentary rock substrates at elevations between 1,280 and 1,330 meters. It is considered rare and threatened because of its narrow distribution and small population size. Currently, it holds a California Native Plant Society Rare Plant Inventory rank of 1B.2. The plant typically blooms from March to May and fruits from May to June. They are commonly used in Butterfly Gardens.

...