Agriculture Reference
In-Depth Information
There are a number of requirements for plants to perform in roof gardens includ-
ing their ability to withstand heat and high temperatures, and exposure to pollutants
and wind. Plant survival can be compromised by a shallow soil media. Changes in
temperature and shading may affect flowering. The increasing use of plants to trap
and absorb both run off and pollutants in inner city parks has been seen as a new
and valuable use of plants. The incorporation of a waste water treatment system
that passes through a well designed garden allows for community use and filtering
of an otherwise source of pollution. For example the creation of absorption beds
connected to run-off areas within street scapes involving hit and miss paving where
porous areas with turf grass to allow storm water to infiltrate are connected to a
reed bed before entry into the groundwater. Horizontal and vertical filtration beds
with gravel and macrophytes typically with members of the
sedge
family (
Cypera-
ceae
), can also accommodate plantings of reeds such as common reed (
Phragmites
australis
) and Giant reed (
Arundo donax
) and members of the rush family (
Junca-
ceae
), as high nutrient absorbers that remove nitrogen, orthophosphates, ammonia
and total soluble salts (TST) and pathogens (Mink et al.
2002
). Other macrophytes
such as
Baumea
spp
.
,
Juncus
spp
.
, and
Cyperus
spp
.
are effective in removal of
phosphorus and prevent their transport into rivers or lakes where they can cause
algal blooms. These systems have been employed by the Melbourne City Council
in Victoria, Australia to manage nutrient inflows to the Ramsar Edithvale-Seaforth
wetlands in the Port Phillip and Western Port Bays (Melbourne Water
2013
). Float-
ing reed beds on Gold Coast, Queensland, are also used to manage high nutrient
levels (Anon
2013b
).
Living wall gardens
There is an increasing use of plants as living walls that have
been shown to provide environment benefits, such as noise barriers, aesthetics,
wind, pollution, and insulation of buildings when used in association with these
structures and do contribute to the longer term sustainability of the urban environ-
ment. These can take the form of trees such as the Australian native plant drooping
she oak (
Allocasuarina
verticillata
) or
A. cunninghamii
, the
Melaleucas
and
Grevil-
leas
as well as the woolly bush
(Adenanthos sericea).
All make excellent barriers
depending on the height to be screened or as a plant growing on artificial structures.
In the case of a vertical greening system plants such as common ivy (
Hedera
helix
)
creepers (Ottelé et al.
2010
), aromatic plants such as the true myrtle (
Myrtus com-
munis
) and the Australian native lilac (
Hardenbergia comptoniana)
all make good
natural barriers and can soften a building's facade. Stress tolerant plants such as
those from the Mediterranean region can be more successful in reducing the energy
requirements in managing these plants.
A number of plants have been introduced into Australia from overseas as hedge-
row plants or as green cover. The red barberry (
Berberis thunbergii
) is a native to
Japan and eastern Asia, generally hardy, deciduous and tolerant of pollutants. There
are well over 30 cultivars available of
Berberis thunbergii
including a reddish-purple
leaved “Harlequin” and the yellow “Aurea” forms (Missouri Botanic Gardens
2012
,
Vandeputte
2012
, Wiley De Nolf
2012
). The red barberry grows 1 to 1.2 m and toler-
ates cool temperate conditions and has proven to be very popular plant in Europe.
