Green wall plants
Depending on the scale of the wall, plantings can range from ground covers to larger herbaceous species, shrubs and even small trees.
Plant selection should firstly consider the desired outcomes of the green wall. Certain plants will be better for aesthetic and landscape design values, drought tolerance, water purifying, air filtering or habitat provision. It is important to realise that plant growth form, sun and shade exposure as well as wind exposure, is notably different on vertical surfaces compared to a roof or at ground level. Obtaining specialised advice and visiting existing green walls will improve understanding of which species will be best suited.
The selection of species will also depend on the climatic conditions on-site. Consider the level of natural or artificial light available. (Be aware that plant selection will require an understanding of ‘photosynthetically active radiation’, the type of light that a plant responds to, rather than simply a measure of how the human eye perceives brightness). Select very shade tolerant species to suit the lowest light conditions. In highly exposed locations, select robust species that can tolerate sun and wind. Look for species that have shallow, fibrous root systems to promote strong anchorage in the limited volume of growing medium available. Recognise that the tops, corners and sides of the wall will have greater wind exposure. Investigate species that thrive in exposed conditions, such as coastal cliffs or inland rocky outcrops.
Larger plants may grow to shade others, so this must also be considered in the placement of species. External green walls are often exposed to strong and frequent wind. Vigorous growth increases maintenance requirements and slow growing plants are often preferred. However, vigorous species can be used to create protected niches for the inclusion of sensitive species in high exposure areas. This can help provide light or shade for other species, wind protection or humidity conservation. Consideration of where each species will be placed in relation to others (the array of plants) helps develop a working artificial ecology on the wall. Understanding how the ecology will morph as the plants mature is important, as niches will evolve beneath, next to and above certain species.
Plant selection must be matched to the particular green wall system and technology that is being installed. Not all species will grow well in each system. Some systems might cater well for terrestrial plant species (and need an appropriate growing substrate); others have an irrigation/fertigation or growing media system that favours epiphytic/lithophytic species (plants that do not require soil for growing and can exist on branches or rock surfaces).
Water requirements can be minimised by selecting species that are low water users. Recognise that more water may be available toward the base of a green wall system, so species should be selected and positioned on the wall with moisture gradients in mind. If the system recycles water, species selection may have to cater for elevated salt levels and amended pH levels.
Suitable plants for green walls in Victoria
Provided as a guide only, and should not be considered as an exhaustive list or suitable for all sites
|Shrubs||Correa cultivarsEscallonia cultivarsFicus speciesMetrosideros excelsa ‘Nana’|
|Evergreen herbaceous perennials||Spathiphyllum cultivarsPhilodendron ‘Winterbourn’ and ‘Xanadu’Monstera speciesLiriope species and cultivarsSchleffera species
|Herbaceous ground covers||Epipremnum speciesPlectranthus ciliatus|
|Ferns||Asplenium speciesBlechnum species Davallia pyxidataHumata tyermaniiNephrolepis species|
|Grass-like foliage forms||Acorus gramineus cultivarsBulbine speciesFicinia nodosaDianella speciesDietes species
Lomandra species and cultivars
|Lilies & irises||Arthropodium cirrhatum ‘Te Puna’ and ‘Parnel’Arthropodium species
Neomarica gracilisPatersonia occidentalis