Planting trees is an excellent way to provide a screen that will modify or hide the view of adjacent buildings, walls, driveways, parking areas, overhead utilities/fixtures or other unsightly areas. Living screens are also becoming more important since house sizes get larger and taller and house blocks becoming smaller.
Using trees as living screens can easily enhance living and working open spaces. They tend to be more visually appealing and enhance environmental conditions. Screening can be used to define an area, modify views, create privacy, block wind, filter light, and direct traffic flow. A living screen can also be used to separate or define areas with different uses.
Trees planted in the long, narrow corridors between buildings, can break up or reduce wind tunnelling. Buildings with screen trees planted on the prevailing wind side can benefit from energy savings.
Before selecting trees for screening, first determine the screen’s purpose, whether functional or environmental.
Choosing a Suitable Screen
Before selecting any tree, consider characteristics that may change as the tree grows. A little research can prevent the cost and trouble of removing a tree that has become unsuitable for the place where it was planted. A tree’s special characteristics and tolerance of harsh growing conditions determine its suitability for a particular situation.
You need to establish;
How high and dense you need the screen to be and how quickly you need it to do the job.
What are the growing conditions like and how adjacent are buildings and other hard surfaces?
The width of the screen may also be an issue, particularly if planted between houses, or adjacent to fences and pathways. Plants that develop broader canopies may require more, on-going pruning maintenance. Healthy plants need a substantial root system to grow. Provide appropriate below ground space to sustain trees and enable them to meet aesthetic and design expectations. A wider planter space will also allow greater choice of species. If the space is too narrow, climbers or non-living screens may be more suitable than trees.
Give careful consideration to the following factors before selecting a screening tree.
Size at maturity
Determine mature tree characteristics and decide whether these characteristics will be suitable for the planting site when the tree reaches its ultimate height and spread. Select trees that will not grow too big to cause damage to surrounding structures like fences, buildings and driveways. In narrow areas or in beds between buildings and streets, a tree with a small canopy and limited root spread is preferable.
Canopy form and texture
Choose trees with columnar or fastigiate forms (Upright branching, narrow) for restricted/narrow areas, row plantings, or against tall buildings. When planted in rows, trees with a narrow, columnar canopy effectively block an unsightly view, define areas, and act as a barrier. They can be planted close to fences and buildings without hanging over into other areas and can give a building a formal or classical appearance.
Trees with round or pyramidal canopies are effective for areas that have increased root area and adequate overhead canopy area.
Multi-branched trees with large leaves or mass production of small leaves are suitable trees for screens. Species should also be tolerant of pruning. Pruning may be used to increase the density of many screening plants, and is recommended in the management of screens, particularly fast growing species.
Deciduous vs. evergreen screening
For seasonal screening, select deciduous trees. Deciduous trees will provide shade during the summer, but will allow more light in during the winter.
Evergreen trees provide more permanent screening, however, consider how dark an area is during the winter months if you use a dense evergreen screen.
Many species of trees, shrubs and climbers make excellent screens. Usually mass plantings of the same species are used, although screens may use a mix of different plants.
Callitris rhomboidea (Port jackson Pine, Oyster Bay Pine) Australian native conifer. Narrow large shrub to small tree to 6m tall. Good drought tolerance.
Chamaecyparis lawsoniana (Lawson’s Cypress varieties) Conical to columnar tree. Height will vary dependent on variety.
Chamaecyparis obtusa ‘Crippsii’ (Golden Hinoke Cypress). Conical small tree, 3-6m.
Cupressus glabra ‘Hodginsii’ (Blue Arizona Cypress). Compact, columnar tree to 10m.
Cupressus sempervirens ‘Totem’ (Italian Cypress var.). Upright columnar tree 10-15m.
Cupressus torulosa (Bhutan Cypress). Medium to large tree with pyramidal to conical form.
Juniperus chinensis ‘Spartan’ (Chinese Juniper var.). Tall, narrowly conical tree to 6m.
Thuja orientalis (Bookleaf Cypress varieties). Conical to ovoid small trees and shrubs. Height will vary dependent on variety.
Thuja plicata ‘Fastigiata’ (Western Red Cedar). Tall columnar to conical tree 15-20m.
Australian native trees
Acmena smithii var. minor (Lilly Pilly). Small tree, bronzy new growth 3-6m
Acmena smithii ‘Hot Flush’ (Lilly Pilly var.) Up to 3m with moderate growth habit and reddish new growth.
Acmena smithii ‘Sublime’ ?(Lilly Pilly var.). Small tree large shrub with lime green new growth. Up to 3-5m
Callistemon viminalis ‘Hannah Ray’ (Weeping Bottlebrush var.). Small tree, large shrub 3-4m tall with pendulous branches.
The following are varieties of Scrub Cherry (Syzygium australe).
Syzygium australe ‘Aussie Southern’ 3-4m
Syzygium australe ‘Elite’ 3-5m
Syzygium australe ‘Pinnacle’?Very narrow habit 3-5m
Syzygium ‘Aussie Northern’ Compact to 4-5m
Acer campestre (Hedge Maple) Deciduous medium tree 8-10m. Use varieties ‘Queen Elizabeth’ or ‘Elsrijk’
Camellia sasanqua (Sasanqua Camellia). Recommend varieties; ‘Edna Butler’, ‘Hiryu’, ‘Jennifer Susan’, ‘Plantation Pink’, and ‘Snowcloud’.
Gleditsia triacanthos var. inermis ‘Elegantissima’ (Thornless Honeylocust var.) 3-4m
Photinia x fraseri (Fraser Photinia). Large shrub to small tree with burgundy-red new foliage which contrasts nicely against the dark green mature foliage, 4-5m.
Pittosporum tenuifolium ‘Screen Master’ Fast growing plant, 4-5m
Prunus cerasifera ‘Oakville Crimson Spire’ ?Upright form of purple leaved flowering plum. Up to 6m.
Pyrus calleryana ‘Capital’ (Callery Pear var.) Deciduous, columnar tree to 12m.
Bamboos (Clumping varieties)
Bambusa textilis (Slender Weaver) – 10m
Bambusa textilis ‘Gracilis’ – 6m
Bambusa eutuldoides var. viridi vittata (China Gold) – 6m
Bambusa multiplex var. ‘Alphonse Karr’ (Alphonse Karr) – 4m
Bulleen Art and Garden 2008, Bulleen Art and Garden, Bulleen, Victoria, viewed 6th May 2008.
Spencer, R. (1995) Horticultural flora of south-eastern Australia, Volume 1, Fern, Conifers and their Allies. University of New South Wales Press.
Virginia Cooperative Extension. 2008, Trees for Problem Landscape Sites -Screening, viewed 6th May 2008.