Tropical evergreen and semi evergreen forests constitute 74.6% of the total area of Periyar Tiger Reserve, followed by moist deciduous forests that form 12.7% and grasslands which are 1.5% and eucalyptus come under 7.1% of the area. Periyar Lake constitutes the rest of the area i.e., 3.5%.

Floral diversity
Angiosperms 1966 Spp.
Gymnosperms 3 Spp.
Pteridophytes 170 Spp.
Medicinal Plants 350 Spp.

Pectelis gigantea
-a threatened ground orchid
Endemic Plants of PTR
1 Mucuna pruriens thekkadiensis
2 Habenaria periyarensis
3 Syzygium periyarensis

1 West coast tropical evergreen forests Vateria indica, Cullenia exarillata, Hopea parviflora, Canarium strictum, Thottea siliquosa, Calamus vattayila, Gnetum ula, Impatiens parasitica … etc.

2 West coast semi-evergreen forests Artocarpus hirsutus, Bischofia javanica, Myristica dactyloides, Psychotria thwaitessii, Strobilanthus ciliatus, Jasminum flexile, Mucuna hirsuta … etc.
3 Southern moist mixed deciduous forests Tectona grandis, Dalbergia latifolia, Grewia tiliifolia, Pterocarpus marsupium, Lagerstroemia microcarpa, Desmodium pulchellum, Helicteres isora, Pavetta indica… etc.
4 Southern hilltop tropical evergreen forests Syzygium gardneri, Litsea oleoedes, Hydnocarpus alpina, Drypetes wightii, Actinodaphne bourdilloni, Agrostistachys borneensis, Amomum muricatum … etc.
5 Southern montane wet temperate forests Actinodaphne campanulata, Rhododendron arboreum, Vernonia travancorica, Garcinia cowa, Syzygium parameswaranii, Symplocos pulchra ... etc.
6 South Indian sub-tropical hill savannahs Terminalia chebula, Careya arborea, Phyllanthus emblica, Themeda cymbaria, Chrysopogon hackelii … etc.
7 Southern wet montane grasslands Phoenix loureirii, Strobilanthus kunthianus, Hypericum mysorense, Arundinella ciliata, Tripogon bromoides… etc.