They work well indoors and out with stunning results. There are some great examples in Paris created by the famous vertical wall garden designer, Patrick Blanc. One covers this museum, near the Eiffel Tower, and the greenery also reflects on adjacent glass buildings. Using recycled water and solar powered lighting such installations are day/night attractions. Plants don’t always need soil to grow. They grow well in rocks, tree trunks and bare slopes in tropical forests or temperate mountain areas. They can grow out of felt stapled on to a pvc sheet attached to a metal frame. The water is provided automatically from the top and is supplemented with nutrients.