Symbolism, Imagery, Allegory
Shmoop loves throwing Latin terms at you: it's so...scholarly. It builds character. And in this case, it also can't be avoided.
The idea of the hortus conclusus as a literary image has biblical origins and divine implications. It means "enclosed garden" and comes from a verse in the Song of Songs (4:12): "A garden enclosed is my sister, my spouse; a garden enclosed, a fountain sealed up." The lyric is a bridal song and is understood by Christian writers as a reference to Mary, the mother of Jesus, because she is believed to have been born without original sin and a perpetual virgin.
The hortus conclusus went from concept to reality in medieval landscape architecture. These gardens were actually walled in (and might even have a door with a lock), private and safe places to enjoy oneself. As in the biblical verse, they usually had a fountain in the middle of them, just like the one enjoyed by the crew in The Decameron.
The enclosed garden seems to represent the inviolability of the space where the brigata have retreated. They're protected from the ravages of the plague; they forbid news from the outside world. They're creating their own little world, if only for ten days. What's interesting is that within this walled up and protected space, a lot of walls come tumbling down. Inhibitions disappear, at least in the storytelling. But we have the sense that it's the walled garden that makes this seem safe and possible. What happens in the hortus conclusus stays in the hortus conclusus.
The image of the hortus conclusus is everywhere in medieval art and literature. Take a look at some of the beautiful images from the manuscripts of this period and you'll see what we mean. Even better, take a trip to the Cloisters in New York and see the hortus conclusus in action, both in the living garden there and in the spectacular tapestries that are part of the permanent collections.
The hortus conclusus is above all things, a place of pleasure, which makes it a locus amoenus—the "pleasant place" of ancient poetry. A locus amoenus, strictly speaking, doesn't have to be a cultivated garden. But it usually has three elements: trees, grass, and water. It should be away from the busy city, a peaceful hideaway where you can escape from the pressures of time and contemplation of human mortality (i.e., staring at piles of your neighbors' rotting corpses). It's more than just a beautiful place, though—it's idyllic, like the Garden of Eden.
The brigata desperately needs a locus amoenus to escape not only the filth and contagion of the city, but also the psychological stress brought on by the sadness, fear, and loneliness of the loss of family, friends, and normal life. They find more than one "pleasant spot" in their vacation place when they scope out the Valley of the Ladies and spend a day storytelling there.