The term gardenesque was introduced by John Claudius Loudon (1783–1843) in 1832 to describe a style of planting design in accordance with his 'Principle of Recognition'.
Loudon was worried that picturesque planting could be mistaken for natural growth and argued that for a planting design to be recognizable as a work of art only exotic plants should be used.
Later in his career Loudon accepted several other ways of making planting recognizable as art (1) by removing surrounding plants so that a perfect form of the plant was grown (2) by 'high keeping' (intensive maintenance) in a garden (3) by planting in geometrical beds.
Though Loudon was clear about his reasons for introducing the gardenesque he gave varied accounts of how the principle could be satisfied.
[1]The OED then gives several quotes illustrating various usages of the term: The use of the word gardenesque in UK business has been trademarked by the British e-commerce brand Gardenesque.com.