Swl. Jacobs et al., LUDWIGIA PERUVIANA (ONAGRACEAE) IN THE BOTANY WETLANDS NEAR SYDNEY, AUSTRALIA, Australian Journal of Marine and Freshwater Research, 45(8), 1994, pp. 1481-1490
Ludwigia peruviana is an aquatic shrubby species introduced from the A
mericas and spreading to wetlands in coastal south-eastern Australia.
It has become dominant, replacing much of the former vegetation in the
Botany Wetlands, a series of shallow urban swamps and lakes near Sydn
ey, Australia. Studies of L. peruviana were essential to the developme
nt of a management plan for the Botany Wetlands. Ecological studies we
re conducted in situ and supplemented by a series of germination and g
rowth experiments in controlled environments. Flowering peaked in earl
y autumn. Seed production for 1990-91 was similar to 450000 seeds m(-2
) and there was also similar to 65000 seeds m(-2) in the soil seed ban
k and similar to 300000 seeds m(-2) in old fruits that remained on the
stems over winter. The seeds are similar to 0.8 mm long, weigh simila
r to 0.05 mg, are hydrophobic, usually germinate while afloat, and are
easily dispersed by water, machinery and birds. Viability of fresh se
ed was 99% (tetrazolium dye test), and similar to 20% of seeds were do
rmant. Dormancy appeared to break down within two years. Propagation a
nd dispersal may also occur by means of stem pieces that produce new s
hoots. New plants from seed, seedlings or stem fragments may become es
tablished on strand lines or form floating islands that may eventually
become stranded. Management needs to focus on control of the seedling
s and soil seed bank.