Strictly coastal, growing in recently disturbed habitats, such as around slip scars, within petrel colonies, on talus slopes, and under open coastal scrub and forest. At Mayor (Tuhua) Island it is associated with an old pa site. The seed is long-lived, and has a persistent seed bank, such that this species often appears following major habitat disturbances caused by storm damage or fire
A naturalised race of Hibiscus trionum is often confused with H. richardsonii (see de Lange et al. 2010; Craven et al. 2011). It has larger, more deeply divided and lobed leaves, much larger pale-yellow to yellow flowers which open fully, petals which are consistently and distinctly basally blotched dark brown, purple-red or maroon, and larger seeds.
http://www.nzpcn.org.nz/flora_details.aspx?ID=2318