It has always puzzled me as to why the Garden of Epicurus was refered to as "Kepos" -- and perhaps there was something in the minds of people at his time which we don't fully grasp.
Looking at Greek mythology there is the garden of Hera, also called Garden of the Hesperides.
From the internet: "The Garden of the Hesperides is Hera's orchard in the west, where either a single apple tree or a grove grows, producing golden apples." (Wikipedia)
"The Golden Apples in the Garden of Hesperides were a wedding gift to Hera from Gaia and were protected by a great serpent called Ladon. The Apples as well as the rest of the life in the Garden were tended by the Hesperides, minor earth goddesses or nymphs and daughters of the Titan, Atlas."
"The Garden itself was completely ruled by the Olympian gods and goddesses, therefore completely inaccessible to mortals. To complete his twelve labors, Hercules was sent to the garden to retrieve three of these golden apples for King Eurystheus."
"To find the exact location of the Garden of Hesperides, Hercules had to pry the information from Nereus, the Old Man of the Sea, encounter and free Prometheus, kill Ladon, and implore Atlas to pick the apples for him. Eager to sit aside his burden of holding up the heavens, Atlas convinced Hercules to take up the heavens in his place before deciding to take the apples to Eurystheus himself and leave Hercules there. Hercules tricked him by claiming he needed to make a pad for his shoulders to hold the heavens up more comfortably, asking Atlas to take them up again for a moment. When Atlas held the heavens again, Hercules snatched the apples from him and left. After this long adventure to get the apples, Athena rather anticlimactically took the Apples from Eurystheus and returned them to the Garden."
So thinking further on how this mythical garden was thought to be inaccessable to mortals, in contrast we have "Kepos" and this could give some indication as to the nature of the Epicurean garden -- and the Epicurean hope that mortals could live as blissfully as the gods.
Also I looked up on cultivation of apples, and found this, which says they were cultivated in ancient Greece (source).
So perhaps there was an apple tree in the Kepos