what is a "floating gardener"?

They enter busy Gup City. Iff finds out that all units have been ordered back to base, but he did not get the message. A strange looking weed comes speeding along beside their boat. Butt tells Haroun that it is “A Floating Gardener,” and the weed transforms itself into the likeness of a person right before Haroun’s eyes. It runs across the surface of the water showing no signs of sinking. Mali, the Floating Gardener, untwists the stories in the water. Iff explains that as the stories grow longer, they also become twisted and braided. Mali tells Haroun that the pollution in the ocean is become very bad. “Certain popular romances have become just long lists of shopping expeditions. Children’s stories also. For instance, there is an outbreak of talking helicopter anecdotes.”