The mountain hosts a diverse range of plant species, including Dipteris conjugata, Dicranopteris linearis, Machaerina falcata, Freycinetia storckii, and Davallia epiphylla.

Among these, Dipteris, a fern with leaves resembling those of Tacca, is notably rare in the Samoan Islands and has been recorded only on Mount Matafao and Rainmaker Mountain.

Machaerina is a large sedge, while Freycinetia is a coarse-leaved climbing or scrambling vine also found in the cloud forests of Taʻū Island.

The mountain also supports a variety of tree species, including Pandanus reineckei, Rapanea myricifolia, Syzygium brevifolium, Astronidium, Spiraeanthemum samoense, Alstonia godeffroyi, Eurya japonica, and Weinmannia affinis.

Two species, Astronidium and Cyrtandra geminata, are entirely restricted to the trachyte plugs of Tutuila Island, highlighting the ecological and conservation significance of Mount Matafao.