Question: In which county is the botanical gardens of which, The Desert Garden Conservatory, is part ?

Context paragraphs:
Desert Garden Conservatory: The Desert Garden Conservatory is a large botanical greenhouse and part of the Huntington Library, Art Collections and Botanical Gardens, in San Marino, California.  It was constructed in 1985.  The Desert Garden Conservatory is adjacent to the 10 acre Huntington Desert Garden itself.  The Garden houses one of the most important collections of cacti and other succulent plants in the world, including a large number of rare and endangered species.  The 3000 sqft Desert Garden Conservatory serves The Huntington and public communities as a conservation facility, research resource and genetic diversity preserve.  John N. Trager is the Desert Collection curator.

Mirijjawila Botanical Garden: Mirijjawila Botanical Garden is one of the five botanical gardens in Sri Lanka.  The other botanical gardens are Peradeniya Botanical Garden, Hakgala Botanical Garden, Henarathgoda Botanical Garden and Seetawaka Botanical Garden.

Huntington Desert Garden: The Huntington Desert Garden is part of The Huntington Library, Art Collections and Botanical Gardens in San Marino, California.  The Desert Garden is one of the world's largest and oldest collections of cacti, succulents and other desert plants, collected from throughout the world.  It contains plants from extreme environments, many of which were acquired by Henry E. Huntington and William Hertrich (the first garden curator) in trips taken to several countries in North, Central and South America.  One of the Huntington’s most botanically important gardens, the Desert Garden brought together a group of plants largely unknown and unappreciated in the beginning of the 1900s.  Containing a broad category of xerophytes (aridity-adapted plants), the Desert Garden grew to preeminence and remains today among the world’s finest, with more than 5,000 species in the 10 acre (4 ha) garden.

Huntington Library: The Huntington Library, Art Collections and Botanical Gardens (or The Huntington) is a collections-based educational and research institution established by Henry E. Huntington (1850–1927) and located in Los Angeles County in San Marino, California, on the western coast of the United States, and about 35 miles northeast of the Pacific Ocean.  In addition to the library, the institution houses an extensive art collection with a focus in 18th and 19th-century European art and 17th to mid-20th-century American art.  The property also includes approximately 120 acres of specialized botanical landscaped gardens, most notably the "Japanese Garden", the "Desert Garden", and the "Chinese Garden" (Liu Fang Yuan).

Matthaei Botanical Gardens: The University of Michigan Matthaei Botanical Gardens (300 acres, 121 hectares) includes botanical gardens, natural areas with trails, and several research-quality habitats.  The conservatory is popular year round.  The public entrance is at 1800 North Dixboro Road in Ann Arbor, Michigan.  The grounds are open every day, but trails are not maintained in the winter.  The Conservatory, Garden Store, and Lobby are open 7 days a week: Mon., Tues., and Thurs. - Sun., 10:00 am–4:30 pm; Wednesdays 10 am-8 pm.  The building complex is only closed on three holidays a year.  The institution's main web site with updated information is Matthaei Botanical Gardens.

Walter Sisulu National Botanical Garden: The Walter Sisulu National Botanical Garden ("previously known as the Witwatersrand National Botanical Garden") is a 300 ha botanical reserve in Roodepoort near Johannesburg.  Formally established in 1982, it is one of the youngest of South Africa's National Botanical Gardens, but the site where it is located has been popular with visitors for many decades before that.  The garden is home to a well known pair of Verreaux's eagles that nest in the Roodekrans ridge which intersects the reserve.  The garden has a restaurant, gift shop and nursery which sells South African native plants (the nursery closed March 2015).  The Garden has been recognized as one of the most beautiful botanical gardens in the world.

Beaumont Botanical Gardens: The Beaumont Botanical Gardens (23.5 acres), also known as the Tyrrell Park Botanical Gardens, includes botanical gardens and the 10,000 sq ft "Warren Loose" "conservatory".  The gardens are located in 500 acre Tyrrell Park at 6088 Babe Zaharias Drive, Beaumont, Texas, USA.  An extra benefit is that the gardens are located in a migratory bird flyway.  Tyrrell Park is listed on the Great Texas Coastal Birding Trail map.

Nanjing Botanical Garden, Memorial Sun Yat-Sen: The Nanjing Botanical Garden Memorial Sun Yat-Sen (), established in 1929, became the first national botanical garden in China.  The original name, 'Botanical Garden Memorial Sun Yat-Sen', commemorated Dr. Sun Yat-Sen, the pioneer of Chinese democratic revolution.  In 1954, it was renamed as Nanjing Botanical Garden Mem.  Sun Yat-Sen, Chinese Academy of Sciences.  It is one of four major botanical gardens in China.  The botanical garden is also known as Zhongshan Botanical Gardens after the spelling of its name in pinyin.

Vallarta Botanical Gardens: The Vallarta Botanical Garden is a 64-acre (26 ha) botanical garden at 1,300 ft (400 m) above sea level, near Puerto Vallarta).  The garden was founded in 2004 and has been open to the public since 2005.  The collections showcase plants of the Tropical Dry Forest Biome, native to the region around Puerto Vallarta and in which the Gardens are located, as well as exotics from around the world.  Orchid conservation and propagation is a focus of the garden's mission.  These can be found on trees throughout the grounds and in the Holstein Orchid and Vanilla House.  Other notable collections include oaks, bromeliads, agaves, cactus and wild palms.  The Vallarta Botanical Gardens actively participates in public environmental education through tours and classes.  The Vallarta Botanical Gardens were selected in 2013 as one of the "Top 10 North American Gardens Worth Travelling For" by the North American Garden Tourism Conference's International Tourism Award Jury (a program managed by the Canadian Garden Council.)

Wahiawa Botanical Garden: The Wahiawa Botanical Garden, 27 acre is a botanical garden on a high plateau in central Oʻ ahu, Hawaiʻ i, United States, located between the Wai'anae and Ko'olau mountain ranges.  It is one of the Honolulu Botanical Gardens, and home to a collection of tropical flora requiring a relatively cool environment, with emphasis on native Hawaiian plants.  It is nicknamed the "tropical jewel" of the Botanical Gardens.  The Garden's site began in the 1920s, when the Hawaiian Sugar Planters' Association leased land from the State of Hawaiʻ i for experimental tree planting.  Most of the Garden's large trees date from that era.  The property was transferred to Honolulu in 1950, and opened as a botanical garden in 1957.  It is open seven days a week, from 9am to 4 pm.

Supporting paragraphs: Desert Garden Conservatory Huntington Library
Answer: Los Angeles County