The valley basins between the Spenser Mountains and around the lakes are mainly covered with red (Nothofagus fusca) and silver beech (Nothofagus menziesii) with scattered cases of totara (Podocarpus totara), all up to 1500 m above sea level. Interestingly, beech species seem to dominate over altitudinal zones, whereas red beech is most dominant in lower levels, then silver beech and lastly mountain beech (Nothofagus solandri cliffortiodes). Black (Nothofagus solandri) and hard beech (Nothofagus truncata) may be found around the lakes of Rotoroa and Rotoiti.
The layer of vegetation beneath the main canopy of these forests contains several other trees, herbs, shrubs, and ferns that are densest where beech species are uncommon. These include fuchsia (Fuchsia excorticata), wineberry (Aristotelia serrata), marble leaf (Carpodetis serratus), rata (Metrosideros umbellata), rimu (Dacrydium cupressinum), kahikatea (Dacrycarpus dacrydiodes), matai (Prumnopitys taxifolia), miro (Prumnopitys ferruginea), manuka shrub (Leptospermum scoparium) and many Coprosmosa species.
The sub-alpine territory above the tree-line is home to smaller shrubs (Dracophyllum townsonii/genus Phyllocladus), flax (genus Phormium), grasses (genus Chionochloa), herbs, cushion plants (genus Raoulia), tussock as well as some alpine flowers (genus Senecio/genus Celmisia).