[www.iucngisd.org] Ecological impact, invasiveness: Law (2003) report that, "G. tinctoria shades out rare and endangered indigenous flora and fauna. The huge leaves of each G. tinctoria mean it can impact on a disproportionately large number of the comparatively small, native herbs. Areas that have been cleared of mature G. tinctoria can become re-colonized with numerous seedlings from the original plants, and pieces of the rhizomes that break off will also re-grow. In areas with harsh winter frosts, G. tinctoria is deciduous or semi-deciduous. Once established, it is very invasive and forms dense colonies that shade-out or suppress desirable flora. These characteristics have contributed to it being a serious threat to indigenous biodiversity values in areas it has invaded ". Weedbusters (2003) report that G. tinctoria can block drains and streams; and obstruct access to natural and recreational areas. (link added by Mary Ann Machi)