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GRAANGIDS
2016
GRAIN GUIDE
Acacia saligna (Labill.) H.L. Wendl
The Port Jackson willow is indigenous to Australia and is described as a perennial shrub or small
tree that can grow to between 3 m and 7 m tall. It grows in a variety of soil types and occurs
particularly in disturbed areas or road reserves. It has an extensive root system comprising a
well-developed taproot and several shallow, lateral roots. This tree grows rapidly and its useful
life is between 15 and 20 years. Many seeds are produced per plant and they are also the main
propagation mechanism.
The negative aspects of the Port Jackson willow include the
following: It competes for light, space, water and nutrients; it
displaces indigenous vegetation quickly; it changes the land-
scape and habitat; contaminator (seed); obstruction – dense
stands limit the movement of animals; in water and river courses
it causes an obstruction to water flow; obstruction in terms of
vision; consumes large quantities of water; reduces grazing
capacity and biodiversity if dense stands occur. A rust fungus and
seed-eating snout beetle act as biological control agents against
the plants – the bio-agents are very effective and should be
employed as first control mechanism. Although very hot fires can
cause the tree to die, it is not recommended as control method
as fire will promote seed germination. Mechanical control alone
is not recommended, as sprouting will occur. Various chemicals
are registered to control the plant and can be useful in combina-
tion with mechanical control. According to the CARA Act the Port
Jackson willow is classified as a category 2 plant – it may occur
only in a defined area if permission for this has been obtained.
(Any plants outside the defined area must be controlled.) If the
landowner does not have permission, it must be controlled.
Lantana camara L.
Lantana originally comes from Central and South America. It is an erect to spreading thorny
shrub. It has a well-developed root system and does not display specific habitat preferences – it
therefore occurs in various areas in a variety of soil types. Propagation of the lantana is usu-
ally through seeds that are often disseminated by birds, but new plants can also develop from
the rhizomes. It is globally regarded as one of the major weed species. The negative aspects of
lantana are the following: It competes for light, space, water
and nutrients; it displaces grasses; it inhibits the growth of
grass (is allelopathic); it changes the landscape and habitat,
particularly if it occurs in dense stands; it is toxic to animals; it
is thorny; contaminant (seed); obstruction (access, cultiva-
tion, vision); increases erosion; reduces soil binding; forms
impenetrable stands; reduces the grazing capacity and bio-
diversity if in dense stands. Various biological control agents
were released on lantana, but the success of the bio-agents
varies, as more than 50 different types of lantana occur. Fire
as control measure is not effective, as aggressive sprouting
will occur afterwards. Mechanical control should be applied
only in combination with chemicals, as mechanical control
alone also causes sprouting. Various chemicals are registered
for controlling the plant. According to the CARA Act lantana is
a category 1 plant – the landowner must therefore control it.
Acacia saligna
Lantana camara
Continued on p. 82