Camellias, originally from China and Japan, were introduced in the Park of Pena by Ferdinand II, in the 1840s. Planted by the French gardener Bonnard and supplied by the most prestigious European nurseries, the Garden of Camellias features, in addition to international cultivars that were fashionable during the 19th century, many Portuguese cultivars, notably the collection of 18 cultivars of Camellia japonica that represents a genealogical tree of the nation founding House of Bragança, cultivated by Marques Loureiro, a horticulturist from Porto. The collection proved an award winner when picking up the first-class medal in the International Exhibition held in Porto’s Cristal Palace in 1865. To these, others were added, named in homage to various personalities from the 19th century court, the Arts and other events from down the long course of Portuguese history.

In 2023, a new collection was added to the existing one, including 10 hybrids of Camellia azalea, of Chinese origin. This species is native to a remote area located in the mountainous region of Guangdong Province, China. It was discovered in 1985 and is listed on the IUCN Red List as being in Critical Danger of Extinction. This species stands out from other camellias for having a longer flowering period, from May to February, with vibrant red and pink flowers, simple, with petals slightly split at the end, and distributed on the stem in a way similar to that of azaleas. This unique collection was acquired by Parques de Sintra from the nursery of António Assunção (Park Flavius), a specialist in camellias, and enhanced the original collection in the Park of Pena.

Ever since 2009, Parques de Sintra – Monte da Lua, S.A. has advanced with the study, classification and restoration of the extensive camellia collection in the Park of Pena, which includes 3,858 specimens primarily concentrated into four key locations: the Garden of Camellias, the Garden of Queen Amélia, the Garden of the Countess of Edla and the Tea Hill. This inventory included the mapping of the specimens using geographic information systems and the botanical identification of both the different species as well as the respective cultivars featuring in the collection. Currently, the gardens contain a total of 441 cultivars belonging to 37 different species.