The Blue Rush, Juncus glaucus, is only one of some 400 species of rushes. It is a European native and grows happily at the edges of ponds. It’s hardy in USDA zones 4 to 11, and is semi-evergreen. It was named for the beautiful blue-green color of its leaves, and is an increasingly popular choice for water gardens.
Butterflies and Moths
Moths and butterflies, when they are in their larval form, will eat rushes. Caterpillars are voracious feeders, and even a light infestation can leave disfigured plants in the garden. Fourteen Coleophora species feed exclusively on rushes, although none are known to prefer Blue Rush more than other types of rushes.
Deer and Rabbits
Surprisingly, Blue Rush plants are not very attractive to either rabbits or deer; in fact, they are sometimes listed as deer-resistant. This makes them a good choice for water gardens in areas where these animals are a problem for gardeners. Of course, a very hungry deer will eat food it normally avoids, so protection might be necessary during really harsh winters.
Most marsh plants are not eaten by plants or insects. About 90 percent of the biomass of marsh plants decomposes into microbial biomass, which serves as a food source for various creatures. As such, marsh plants are at the base of a food chain that leads upward to both fish and crustaceans. Rushes are very often planted in constructed wetlands, and they are important in various bioremediation projects, especially treating dilute organic waste.
Other Blue Rushes
The term “blue rush” is often used rather casually to refer to a number of different rush species and cultivars. Some of the plants most frequently called Blue Rush are Juncus inflexus, "Blue Arrows"; Juncus patens, "Elk Blue"; and Juncus inflexus, "Afro."