A Golden Tree stands among the other living plants, imperishable, unwilting. Its image makes reference to the golden apples of the Hesprides, The Singing Ringing Tree (an East German childrens film shown on British TV in the 1960's and 70's) and Jame George Frazer's The Golden Bough.
Gold is the world's most obvious metaphor of preciousness and incorruptability, making the object priceless yet in other contexts worthless. Douet applied real gold leaf to the leaves of this living tree, which was then planted and tended in the garden.
The Golden Tree is a 'personification', as a pond personifies a bigger body of water, a grove is a forest or wood, or a statue of a nymph the ideal of beauty and womanliness. Formal gardens are full of such balanced classical references.