I would say that the main element that defines the English Garden stile is randomness. Paths are not straight and do not converge, pretty much the same way as they do not in a natural setting. The eye is meant to be enchanted by the diversity of the flora and by the way it combines in arbitrary harmonies. No straight lines and no geometric forms are forced upon the natural setting. Another element is the existence of water. For some reason nature looks more dramatic when water is introduced in the picture. It gives the viewer a more complete palette of sensations.