Growing plants on a vertical surface without soil is actually more natural than with it, because rarely could soil be found on vertical surfaces in nature. Soilless vertical surfaces however, are abundant, and so are plant species that 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'). A soilless surface have characteristics that are important for these plants — for example it provides excellent drainage.
Epiphytic plants are most common in tropical climates where high humidity and frequent rains can support such a growing location. Well known house plants that grow as epiphytes are Asplenium nidus (Bird's nest fern), Platycerum bifurcatum (Staghorn fern), Aeschynanthus radicans (Lipstick plant), and genera from the Araceae family such as Philodendron, Anthurium and Monstera. In our homes these plants are usually grown in pots. But as this easily may cause overwatering they can be seen much more vigorous on a vertical garden that provides drainage as well as regular supply of its needs.
As one approaches an exposed cliff, most of the times lithophytic plants can be found, in almost any part of the world. For example around the mediterranean basin, an area with an unusually diverse flora, the coastal areas and some of the nearby mountain ranges are excellent places to look for these plants as it is easy to find exposed cliffs with shifting growing conditions.
Saxifragaceae is a family of plants often found growing on rocks. It contains genera such as Bergenia originating around the Himalayas, and Heuchera from North America.
Apart from aesthetic preferences and the plants ability to grow in a soilless, vertical location; the selection of plants is based on several factors, for example: What is the local climate like (minimum temperature especially important to know)? How much sun exposure is each area of the surface receiving and how does it change during the year? Is there any particular micro climate — such as high buildings creating strong winds along a wall? Understanding the prevailing growing conditions is essential to make the right decision when choosing plants.
Studying plants that occur in the surrounding natural areas is also a great guidance. Although wild growing species are rarely available in nurseries, it still gives a good indication of what related species or plants with similar hardiness that might be used.
To find the right species and quality of plants there are different possibilities. Sometimes local nurseries can be a great source. There, plants that have been grown successfully for years in the region may be found. But as these nurseries often have a limited variety, it is most of the time necessary to combine with other regional or foreign suppliers to have a larger variety of plants available.
Vertical Garden Design collaborates with growers that can provide a great selection of anything from tropical to mediterranean plants or plants suited for colder temperate climates. Rare and hard-to-find species are ordered from specialist growers to add unique character to the garden. The combination of local nurseries, large-scale commercial nurseries and specialist nurseries offers a satisfying solution for most kind of projects.
As growing conditions change widely in exterior locations, so do the plants that may be used for such a garden. With more variation in plant material it also allows for more variation of the design. For example a sun exposed surface in a mediterranean climate can be made of many typical aromatic mediterranean plants, such as Lavandula, Thymus, Rosmarinus or Salvia. On the other hand, a shadowed surface in the same climate can have an almost tropical touch with species from genera like 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 chose the right species for the right location.
Indoor climate is naturally very similar all over the world. It is characterized by a temperature of around 20° C, low light intensity and many times — low humidity. As for the temperature and low light, similar growing conditions can be found in the tropics, like under the forest canopy where little light filters through. But those conditions are rarely paired with low humidity, which to some extent limits the plant selection for indoor projects.
Many plants adapted to shady environments grow large leaves in order to assimilate the small amount of light that reaches them. Also they have quite modest flowering, although there are exceptions that can make a great contribution to an interior garden. Typical genera used for interior gardens are aroids like Philodendron 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, not only from a botanical point of view, but they can also have great inspirational value. The brief portraits of plants available in the blog, with images from various study trips, focus on the environment and ambiance as much as the characteristics of a plant. Images are continuously published from new and old trips.