The SSSI at Occombe consists of five herb-rich, unimproved meadows, supporting grassland communities which are now restricted both nationally and in Devon due to agricultural intensification. A range of grassland types are represented within the site, from a dry, well-drained sward to poorly-drained marshy areas bordering the stream which runs the length of the site. Numerous wet flushes add further diversity, as does an area of ancient semi-natural woodland and adjacent tall herb fen and carr vegetation which links the unimproved fields.

The majority of the herb-rich grassland is neutral and is characterised by Crested Dog's-tail Cynosurus cristatus and Common Knapweed Centaurea nigra with frequent Heath-grass Danthonia decumbens . Typical herbs of this community are Common Bird's-foot-trefoil Lotus corniculatus , Field-woodrush Luzula campestris and Devil's-bit Scabious Succisa pratensis . Eight species of sedge have been recorded including Spring-sedge Carex caryophyllea and Flea Sedge C. pulicaris . Where the well-drained grassland communities merge into the frequent wet flushes, the vegetation becomes characteristically taller and is dominated by Rough Meadow-grass Poa trivialis and Floating Sweet-grass Glyceria fluitans . Marsh Valerian Valerian dioica , a local plant species in Devon , Ragged Robin Lychnis flos-cuculi and Marsh-marigold Caltha palustris are frequent here, and are also found together with Yellow Iris Iris pseudacorus in the waterlogged streamside habitats. Elsewhere, as the vegetation merges into the damp grassland typical of such meadows of undulating topography, Meadowsweet Filipendula ulmaria and Rushes Juncus spp. become increasingly frequent, the dominant grasses being Yorkshire-fog Holcus lanatus and Tufted Hair-grass Deschampsia cespitosa . An important feature of the site is the number of orchid species which includes the Green-winged Orchid Orchis morio , a very local plant in Devon with a restricted distribution nationally, and the Common Spotted-orchid Dactylorhiza fuchsii , also with a restricted distribution in Devon .