Bushland Weeds Manual - Environmental Weeds Action Network

64
Chapter 5 Broadleaf Herbs, Sedges and Succulents
Case Studies
Euphorbia terracina invading the understorey of Tuart woodland at Bold Park.
Case study 5.4 Typha orientalis – an aggressive coloniser of wetlands
Two species of Typha are known
from Western Australia,
T. domingensis and T. orientalis.
Native to eastern Australia,
T. orientalis is thought to be
introduced in Western Australia and
it is an aggressive coloniser of
wetlands of the Swan Coastal Plain
and Jarrah Forest. Typha
domingensis is native and occurs
only occasionally in the region. The
native and the weed can be difficult
to tell apart.
Typha domingensis has a
leaf blade that does not
exceed 8 mm in width
and a cinnamon brown
female flower spike that
is 5 to 20 mm in diameter
and 6 to 20 times as long
as it is wide.
Typha orientalis has a leaf
blade up to 14 mm wide
with a chestnut brown
female flower that is 10 to
30 mm in diameter and 5
to 10 times as long as it is
wide. Intermediates exist
and expert help is
sometimes required for
identification.
Life-cycle and Reproductive
Biology of Typha orientalis
• Expansion of existing
populations is rapid, occurring
via rhizomes that grow out
from the population each
season. Establishment of new
populations is via seed.
• Typha orientalis can produce
220,000 seed per flower head.
The seed is very light and winddispersed,
often over several
kilometres. Seed also spreads
via water and is moved around
in mud on the feet of birds,
livestock and humans.
• Seed germination generally takes
place from December to April.
• High temperatures (above
20° C) and high levels of light
are required for germination.
Seeds germinate in mud on the
margins of waterways and,
sometimes, under water (less
than eight centimetres deep).
• Once established, seedlings
start producing rhizomes and
the diameter of the plant can
extend to three metres within
the first year.
The program has resulted in a
significant reduction of Geraldton
Carnation Weed invading the
bushland in Kings Park.
Effective management has relied on:
• Recognising, recording and
removing new infestations.
• Revisiting known populations
year after year (for at least five
years) following up previous
work.
(From Dixon 2000)
Cautionary note: The sap in the stems of
Euphorbia terracina is highly caustic and
can cause quite dramatic and painful
inflammations of sensitive skin. If the sap
gets into the eyes temporary blindness is
often reported and in some severe cases
varying vision loss has been reported. When
working with this plant, or any Euphorbia,
care should be taken to minimise direct
contact with the plant. Safety glasses or face
shields and gloves, at a minimum, with fully
enclosed shoes and neck to wrist to ankle
protection is advised.
• Active growth is mainly
through summer and autumn
although in mild climates it can
occur at any time of the year.
• Flowering commences in early
summer and seed is dispersed
from December onwards.
(from Parsons and Cuthbertson 2001)
Establishment and spread of
Typha orientalis at Lake
Forrestdale
A study based on a series of aerial
photographs of Lake Forrestdale
just south of Perth illustrates how
quickly the weed can spread once
established at a site (Watkins and
McNee 1985). The aerial photos
revealed that prior to 1964 no
T. orientalis occurred at the lake,
with the first stand appearing in
1967. By 1976 a fairly large stand
had established on the southern
end of the lake and by 1984
T. orientalis had colonised almost
the entire six kilometres of lake
margin. Dense colonies had in many
places displaced the native rushes
and sedges in the understorey of
the Melaleuca woodland fringing the