Vertical surfaces in nature are mostly soilless, creating well drained growing locations. Many plants thrive in such conditions — on rocks and cliff faces or branches and trunks of trees. These plants are called lithophytes (from Greek lithos 'stone' and — phyton, 'plant') and epiphytes (epi, is Greek for 'on'). VGD's felt based technique imitates these conditions and allows a large variety of plants to be grown on vertical surfaces.
Epiphytic plants are most common in tropical climates where high humidity and frequent rains can support such a growing location. Typical epiphytic house plants are Asplenium nidus (Bird's nest fern), Platycerum bifurcatum (Staghorn fern), Aeschynanthus radicans (Lipstick plant), and aroids such as Philodendron, Anthurium and Monstera.
As with epiphytes, litophytic plants are more frequent in places with high humidity, such as coastal cliffs or next to waterfalls. Saxifragaceae is a family of plants often found growing on rocks, like the Himalayan bergenias or North American heucheras.
Choosing the right plants
Apart from aesthetic preferences and the plants ability to grow in a soilless, vertical location; the selection of plants is mainly decided by local climate and sun exposure. In an urban context these factors can be influenced by tall buildings that generate winds and irregular patterns of sun exposure. Studying local flora gives a good indication of which plants that might be used. Although wild species rarely are available in nurseries, it still tells about the hardiness zone and what related species that can work.
With different climates and a larger variety of plants available, outdoor vertical gardens allow for more variation of the design. For example a sun exposed wall in a mediterranean climate can be planted with aromatic mediterranean plants like Lavandula, Thymus, Rosmarinus or Salvia. On the other hand, a shadowed wall in the same location can have an almost tropical touch with plants of Begonia, Arum, Davallia, Asplenium, and Fuchsia. A vertical garden can be built in virtually any location, except for very cold climates. The key is to choose the right species for the right location.
Indoor climate typically include a temperature of around 20° C and low light levels. Similar conditions can be found under the tropical forest canopy where little light filters through. Many plants adapted to such environments grow large leaves in order to assimilate the small amount of light that reaches them. They also have quite modest flowering, although there are exceptions that flower freely all year long also in modest light levels. Common plants used indoors are aroids like Philodendron, Anthurium and Epipremnum or gesneriads such as Aeschynanthus, Columnea and Saintpaulia, many species of Peperomia and Begonia or different ferns like Nephrolepis and Pteris.
More about plants
Vertical landscapes in nature are an important reference and have great inspirational value. Have a look in the blog for more pictures of plants and landscapes.