This nationally scarce species is the rarest known vascular plant on the reserve and in Britain is limited to ancient woodlands on the shores and tributaries of the Solent.
Other locally distributed ancient woodland specialities include green hellebore (Helleborus viridis), greater butterfly orchid (Platanthera chlorantha) and thin spiked wood sedge (Carex strigosa).
The woods support both hazel dormice and red squirrels, and alongside the bats form a mammal assemblage that is unique to the UK.
Over 530 nest boxes are arranged in two grids that contribute data to the National Dormouse Monitoring Programme (NDMP) and inform the management of the woodlands.
The rides and railway cuttings also provide a valuable habitat for a variety of woodland butterflies including silver-washed fritillary (Argynnis paphia), white admiral (Limenitis camilla) and the dark crimson underwing moth (Catocala sponsa).