Two large eucalypt tree species grow in the forest along the Illawarra Fly. Brown Barrel, or Eucalyptus fastigata, is the most common, with rich brown bark on the trunk and smooth bark on the upper branches. At maturity level and in ideal conditions they can grow to more than 40 metres. The other large eucalypt species, Gully Gum or Eucalyptus smithii, can be seen near the edge of the escarpment. It has a hard lower bark, with smooth bark higher up that falls off in long streamers and gets caught up in the branches.