In the
Society Islands,
Metrosideros collina is a common canopy tree in montane rain forests above elevation, and in cloud forests from elevation, and on exposed ridges. In the
Marquesas Islands,
Metrosideros collina is common on drier and more exposed montane forests, in cloud forests, and in shrub form in windswept mountaintop shrublands. On
Rarotonga in the Cook Islands,
Metrosideros collina is the dominant tree in
cloud forests on the island's cloud-shrouded peaks and ridges above elevation.
M. collina and associated trees, including
Pterophylla samoensis, Elaeocarpus floridanus, and
Pittosporum rarotongense, form a low forest canopy averaging eight meters tall. In wetter areas and at higher elevations
Ascarina diffusa is often co-dominant or dominant in the canopy.
M. collina is also found in lower-elevation rainforests dominated by
Homalium acuminatum.
Metrosideros collina is a common canopy tree in higher-elevation interior forests on
Pitcairn Island, with the trees
Homalium mouo, Ficus prolixa, Pandanus tectorius, and
Thespesia populnea. ==Varieties==