The hortus deliciarum was a garden of earthly pleasure and was closely connected with the Garden of Eden. This type of garden developed later than the hortus conclusus because it required a stable privileged class and this didn't develop until the 8th or 9th Century, this kind of garden didn't become common until late in the 12th Century. The most famous literary example of this sort of garden is represented by the garden of Deduit (Pleasure) in Le Roman de la Rose, which was written in the 13th Century.
From a design point of view, the two kinds of gardens were similar, both tended to be enclosed by walls. Walls were necessary for security reasons during the entire Medieval period. The difference tended to be in how the gardens were used and in the symbolism attached to the gardens. For example, many Medieval gardens had a pool at their center. In a hortus conclusus this pool was usually a fish pond, while in a hortus delicarum was likely to be a pool for bathing. Also, while both kinds of gardens might contain fountains, the decorations on a fountain in a hortus delicarum were likely to feature imagery of a more secular nature.
Many Medieval gardens were purely utilitarian, but the Medieval world never separated ornamental gardening from the growing of fruits, herbs and vegetables. Orchards were often planted just for growing fruit, but also as pleasure gardens. An orchard which was planted just for fruit was called a pomarium, while an orchard which was planted as a pleasure garden was called a viridarium, the main difference was in how the orchard was used and a viridarium was likely to have an underplanting of flowers.
Flowery meads were common features in both the hortus conclusus and the hortus delicarum. Many gardens consisted of a flowery mead contained by a wall, with turf seats against the wall. A flowery mead was essentially a small scale meadow with flowers planted among the grass, the grass wasn't scythed until the flowers had set seed. Turf seats were raised beds contained by boards, bricks or dressed stone, these were planted with grass and people sat on them. Potted plants were often placed upon these seats.
