Broom is a prolific seeder that spreads rapidly, matures quickly, and colonises large areas, forming pure stands that dominate habitats, causing native plants to be excluded. As it is a legume and can fix nitrogen in the soil, it can change the types of plants which can survive where it has been growing, disturbing the ecology of an area and encouraging further weed invasion. Like Russell lupins, broom holds the gravel together, changing the hydrology of the stream so that fast-flowing channels, unsuitable for wading birds to feed in are formed. Broom also take over the open spaces braided river birds need for nesting, and hides introduced predators like cats and stoats.

Unlike many native species, Broom can tolerate a wide range of conditions and temperatures, being tolerant to frost, shade, and drought. It is not controlled by stock as they don’t like the taste.