Pomaderris hamiltonii is a small tree or large shrub endemic to New Zealand, where it is found in coastal to lowland situations, growing in open successional habitats and shrubland. The population size is small and sparsely scattered along roadsides, drains and coastal slip scars. In 2023 the New Zealand Threat Classification System assessed this species as ‘Threatened – Nationally Vulnerable’ (de Lange et al. 2024). The area of occupancy is estimated to be less than 100km²  and the habitat quality is continuously declining, mainly due to road works and development. There is an estimated decline of at least 30% over three generations (30 years). The species is assessed as Vulnerable.

This species is endemic to New Zealand. It is found on Te Ika a Maui / North Island only near Tinopai, Warkworth / Omaha / Sandspit area, Miranda and on Aotea / Great Barrier Islands. The area of occupancy is estimated to be less than 100km².

The last population estimates for this species were undertaken in the early 1990's, when c. 6,000–9,000 mature individuals were noted, 615 of these at Miranda, the rest in the Warkworth / Omaha / Sandspit Area. Pomaderris hamiltonii was discovered on Aotea / Great Barrier Island in 1992 (Cameron and Cogger 1992) and on Motukaikoura Island (part of the Aotea / Great Barrier Islands group) in 2011 – at both sites the species was described as very uncommon (notably no one has seen Pomaderris hamiltonii at the Aotea / Great Barrier Island 1992 sites since then). Plants were found on the margin of a pine plantation on the road to Tinopai in 2010, and then on the Pouto Peninsula in 2018 – at neither site was it considered common.

Although there have been no further population estimates, Simpkins et al. (2022) considered there to be 1,000–5,000 mature individuals in the Auckland Region, and that these were declining at a rate 10–30% over the next 10 years. The situation at Miranda seems to be even worse, with the species extirpated from 90% of the sites it occupied in the 1990's. Overall, the ongoing rate of decline is estimated to be at least 30% over three generations (30 years).

This is a small tree or large shrub inhabiting coastal to lowland situations, growing in open successional habitats and shrubland. Needing regular disturbance to flourish, this species is now mostly found along roadside cuttings where the constant disturbance provides an ideal habitat, then often found on banks, or on the margins of drains (Wilson and Given 1989, de Lange 2023, de Lange et al. 2024).

The need for disturbance to allow for regeneration is also evident in the seed germination requirements of this species. Pomaderris hamiltonii produced a long-lived seed bank. Sown seed unless treated may take years to germination. Haines et al. (2007) found that P. hamiltonii seed germinated best when the seed was treated in boiling water, sown seed kept warm, and smoke was passed through the potting medium.

The frequently disturbed, open habitats that Pomaderris hamiltonii requires were historically probably fire induced and / or caused by storms opening up coastal and lowland forest. Most of the habitat likely to have been occupied by this species was cleared and converted to farmland and residential areas long before Pomaderris hamiltonii was recognised as a distinct species in 1961 (Allan 1961). Currently the majority of the species' subpopulations are found on roadside cuttings where they are at constant risk from road maintenance crews, roadside spraying, and road widening. Many of the habitats these species occupies are also being cleared for housing. Outside these areas, some subpopulations have been lost through natural succession (de Lange 2023).

This species is occasionally cultivated though rarely sold by plant nurseries.

The roadside habitats, which are the stronghold for Pomaderris hamiltonii need better advocating. Currently those responsible for road maintenance often overlook or forget that this species is threatened and that it grows on land under their care. Road side spraying should cease in the areas occupied by this plant and be replaced with mowing / trimming during times when the species is seeding. This action when it was employed at Miranda in the 1990's increased the Pomaderris population there. This species has an attractive growth habit and flowers, helps stabilize roadside cuttings / banks and does not obscure the roads for road users. Spraying is not necessary; it is merely expedient. Using sprays not only kills P. hamiltonii but also many other attractive indigenous plants that require open habitats to flourish.

In 2017 the New Zealand Threat Classification System assessed this species as ‘At Risk / Naturally Uncommon’ Qualified ‘RR’ [Range Restricted] ‘Sp’ [Sparse] (de Lange et al. 2018). The situation for the species has since worsened, with the stronghold of Pomaderris hamiltonii (the region around Matakana / Omaha / Warkworth) having seen increased housing, and roadworks to the detriment of the species. Populations are being lost rather than rejuvenated. Further, the species has not been possible to locate on Aotea / Great Barrier Island during recent surveys, and the populations on the southwestern side of the Firth of Thames have declined from succession and/or spraying. Combined all this has had a serious negative impact on the species, and in 2023 the New Zealand Threat Classification System re-assessed this species as ‘Threatened – Nationally Vulnerable’ (de Lange et al. 2024).  

Pomaderris hamiltonii is easily grown, flowers freely and so is an attractive garden subject. It should be more widely grown.