Green walls use living plant material on walls to beautify buildings, improve air quality and reduce energy costs.

Ivy covering a building blocks direct summer sunlight, but admits winter sunlight after the leaves have fallen. Modern green walls can provide the same benefit, but avoid the problems associated with having plants growing directly on the building by supporting them on a second, lightweight structure.

There are two kinds of green walls, “green facades” and “living walls.” Green facades consist of planters and trellis-like structures to support climbing vines. On living walls, the plants root in small, soil-filled compartments distributed across the wall, or in some cases in hydroponic mats. Either kind can be used indoors or out.

You might see green walls soon at Red Square in Northeast Minneapolis, and maybe even on Minneapolis City Hall.