From Envirowiki

The Giant Rush is a plant native to the Murray Riverina, which is taking over in some parts, such as Barmah Lake^[1], and becoming a weed species. This is possibly due partially to cattle grazing - the cattle eat the Rush's natural competitors, but not the rush.

[edit] references

1. ↑ http://www.abc.net.au/news/stories/2008/02/19/2166462.htm

• http://www.mdbc.gov.au/subs/information/mfat/wetland/zc_giantrush.htm