Why do you think gardens have always been an intrinsic part of European culture?

The first evidence of an ornamental garden was in ancient Egypt in 14th century BCE. From there there was the first hanging gardens in Syria in 8th century BCE, which was enclosed and called paridesza. The early greek mythology also expressed the quality of harmony and nature. Gardens were first prevalent to express wealth and provide an escape and religious expression for the wealthy. This idea was brought over from the east to the west during the hellenistic period.

Not all gardens in europe are for religious and escape purposes, however, the intrinsic nature of the garden in Europe is mainly for the expression of religion. For example, the Romans used many religious statues in their gardens as well as frescos to depict religious scenes and used as a place to pray and teach about religion.

Image: http://upload.wikimedia.org/wikipedia/commons/e/e9/Italy_by_Frank_Fox_%2848%29.jpeg

Even after the fall of the roman empire and the transition into the Medieval times gardens were used for religious purposes. They used gardens to represent the garden of eden. Most gardens were split into four to symbolize the 4 rivers out of Eden and also planted flowers such as the madonna lily to symbolize Mary and her purity.

Image: http://blog.metmuseum.org/cloistersgardens/2009/04/24/keeping-it-green/cuxa-lawn/

The religious building, such a monasteries, used utilitarian gardens to grow herbs a foods, but they also used gardens such as cloisters for religious teaching purposes. Religion played a large role in European history, and in turn so did the garden. Through the large role gardens played in religion, and the omnipresence of religion of European culture, gardens became an intrinsic part of European culture. 

Image: http://blog.metmuseum.org/cloistersgardens/2009/04/24/keeping-it-green/cuxa-lawn/