Following forest types are recognized inside the park:
- Shola Forests (Southern Montane Wet Temperate Forest)
- Grasslands (Southern Montane Wet Temperate Grassland)
- Transition Forests (Southern Sub Tropical Broad Leaved Hill Forest)
- Evergreen Forests (Southern West Coast Evergreen Forest)
- Shrub Lands
- Deciduous Forests (Southern Tropical Moist Deciduous Forests)
The two distinct physiognomic units of vegetation found within the park are the Grasslands and Shola Forests. These forests are classified as Southern Montane Wet Temperate Forests. The forests on the plateau occupy glens, hollows or valleys. Broadly, the Shola vegetation also includes the Subtropical Broad Leaved Hill Forests that merge into the Evergreen Forests at a lower altitude. Grasslands, Sholas, Shrub Lands and Subtropical Broad Leaved Hill Forests are the major land cover types. A small portion of the park has Southern West Coast Evergreen Forests on its western side and Moist Deciduous Forests on the east.
Around 60% of the area is covered by Grasslands, about 25% by Shola Forests, about 8.45% by Southern Sub Tropical Hill Forest and 7.5% constitute the Shrubs (Menon ARR, 1997).
The characteristics and species found in various forest types.
The hill forests are locally known as ‘Sholas’, the Tamil term for forest. The Shola Forests in the upper plateau are dense and floristically rich with many endemic and rare species. The trees in the Sholas form a continuous canopy usually not exceeding 10-15m. There is no marked differentiation into canopy layers. The tree bark is covered with lichens, orchids, mosses and climbers. The crowns are generally rounded and dense.
Common tree species in the Shola Forests are Pithecellobium subcoriaceum, Ixora notoniana, Syzygium arnottianum, Ilex denticulata, I. wightiana, Michaelia nilagirica, Elaeocarpus recurvatus, Microtropis ramiflora, Actinodaphne bourdellonii, and Symplocos pendula. The edges of the Shola are marked by trees such as Rhododendron arboreumvar. nilagiricum, Ternstroemia japonica, Ligustrum perrottettii, Turpinia cochinchinensis,Mahonia leshenaultii, Rhodomyrtus tomentosa, Berberis tinctoria, Vaccinium neilgherrense etc. and herbs and shrubs include Gaultheria fragrantissima, Moonia heterophylla, Jasminum bignoneacium, Smithia blanda, Valeriana hookeriana and a few species of Strobilanthes. The undergrowth in the Shola is represented by Strobilanthes sp., Impatiens phoenicea, I. coelotropis, Psychotria congesta, Viola patrinii, V. serpens, Asplenium sp., and Arundinaria densifolia. Epiphytic orchids in the sholas include Aerides ringens, Coelogyne nervosa, C. mossiae, Eria dalzelli, E. pauciflora, and Schoenorchis filiformis. The common climbers are Piper schmidtii, Rubia cordifolia, and Connarus wightii. Rapanea capillata, Vaccinium leschenaultii, Impatiens tangachee, Sonerila grandiflora, Osmunda regalis and Eurya japonica are usually found along streams.
Broad Leaved Forests are found on the slopes descending from the plateau. The dominant tree species found in the Broad Leaved Forests are Pittosporum tetraspermum, Elaeocarpus munroii, Apollonias arnotti, Symplocos spicata, Gomphandra coriacea, Garcinia gummi-gutta, Litsea coreacea, Prunus ceylanica and Photinia notoniana. Major shrubs include Begonia subpeltata, Osbeckia lineolata, Polygala arillata, Strobilanthes homotropus, Maesa perrottetiana etc.
About 80% of the park is occupied by Grasslands. They cover the plateau and descending slopes. 308 species are recorded from the Grasslands out of which 51 are endemic to the Montane Grasslands of the Western Ghats (Karunakaran P V., Rawath G S et al. 1998). The major grass species in the Grasslands are Andropogon lividus, Arundinella vaginata, Digitaria wallichiana and Arundinella mesophylla. Chrysopogon zeylanicus and Sehima nervosum dominate these plateau and slopes, whereas in the cattle grazed areas, unpalatable Cymbopogon flexuosus is frequent. Chrysopogon zeylanicus the dominant grass species is found at Rajamala, down slopes of Anamudi and Poovar. Sehima nervosum community is more prevalent throughout the plateau. Moist valleys are characterized by Garnotia sps. Other dominant grasses are Eulalia phaeothrix, Andropogon lividus, Arundinella purpurea, Agrostis peninsularis, Ischaemum indicum, Heteropogon contortus and Tripogon bromodies.
The common herbs and shrubs in the Grasslands include Anaphalis lawii, A. bourneii, A. meeboldii, Swertia corymbosa, Polygala japonica, Curculigo orchioides, Micromeria biflora, Bupleurum distichophyllum, Crotalaria fysonii, C. ovalifolia, Ranunculus reniformis, Hedyotis swertiodes, Senecio lavandulaefolius, Parnassia mysorense, Pedicularis zeylanica, Wahlenbergia gracilifolia, Impatiens pandata, I. modesta, Phlebophyllum kunthianum, Hypericum mysorense, Pteridium aquilinum, Ageratina adenophora, Gaultheria fragrantissima etc. The water logged areas are dominated by species such as Eriocaulon robustum, E. collinum, and E. geofreyii.
The summit of the Anamudi is vegetated with patches of stunted Arundinaria densifolia and Gaultheria fragrantissima (wintergreen), Anaphalis sp., Impatiens and some species of Eniocaulon.
The Shrub Lands in the park form a stable vegetative association occurring on steep slopes below cliffs and interspersed among rock slabs. The dominant Shrub present on the bouldery slopes is Strobilanthus kunthianum, (Neelakurinji). This endemic species blooms once in twelve years. Other species include Ageratina adenophora, Gaultheria fragrantissima, Hypericum mysorense etc. Shrubby species predominate near tea estates and bouldery slopes.
A small portion on the eastern periphery of the park lying close to Talliar estate has Deciduous Forests with trees like Rosewood, Pterocarpus etc. The undergrowth is predominantly Lantana.
Tropical Evergreen Forests
On the western side of the park where the hill forests merge into the Anamudi Reserve, a small segment of the park exhibits characteristics of Tropical Evergreen Forests. The trees are tall and lofty with typical species like Mesua ferrea, Cullenia excelsa and Palaquim ellipticum.