Both Pomona and Rona are bush-clad and are mostly beech forest, with rata, kamahi, totara and miro. Both islands have diverse populations of native orchids.
The vegetation on Pomona island is mixed mountain - silver beech forest with other broadleaf species and lesser podocarps. Miro and yellow-pine are common podocarps, with Hall's totara and rimu also present.
Mountain beech extends from the lakeshore to the summit, while silver beech extends from 400m elevation to the summit. Apart from beech, southern rata and kamahi are the dominant broadleaved species.
In the subcanopy, the treeferns Dicksonia squarrosa and Cyathea smithii are quite common, as well as lancewood and raukawa. The shrubs Coprosma rhamnoides and C. foetidissma (stinkwood) are common shrub species. Supplejack, a native climber, is locally abundant.
The eradication of browsing mammals (deer and possums) has promoted the development of the understory and there has been a radical increase in stem recruitment of many species.
Rona is covered with mixed mountain beech - broadleaved forest. Miro is the most common podocarp, with rimu and Hall's totara occurring less frequently. Kahikatea is found on some moist areas near the shoreline. The main broadleaved species are kamahi, southern rata and lancewood. Native orchids Earina autumnalis, E. mucronata and Dendrobium cunninghamii are common as epiphytes and on the forest floor. The shrubs Coprosma lucida and C. foetidissma are common.
Rona has never had browsing mammals. The diverse plant life has formed deep leaf litter which sustains a rich invertebrate population and has produced an ideal habitat for young kiwi.