Plumwood Mountain is part of the Musgrave Creek sub-catchment, which is one of the least disturbed catchments in the Budawangs. It’s eastern limbs (and from the coast they do look like limbs) drain into the sub-catchments of the Musgrave and Currawan creeks, and then into the Clyde River. The western flank drains into the Mongarlowe River and then into the Shoalhaven.
The geology of Plumwood Mountain is mixed, with Devonian metamorphosed sediments of sandstone and conglomerate in one corner, and a highly fertile basalt strip that runs through the middle, carrying well-developed pinkwood (Eucryphia moorei) rainforest and tall eucalypt (E. fastigata) forest. Plumwood Mountain’s forest types include cool and warm temperate rainforest, tall and wet escarpment forest, dry sclerophyll forest, and teatree scrub.