The sunny south-facing slopes host vegetation adapted to dry conditions, with species such as chestnut oak, scarlet oak (Quercus coccinea), hickories (Carya), and shadbush (Amelanchier). Here also are some locally scarce species; this is one of the few sites in the region were pitch pine (Pinus rigida) is found. The shady, damp, cool gorge bottom and north-facing slopes host hemlock (Truga canadensis), beech (Fagus grandifolia), sugar maple (Acer saccharum), and mountain maple (Acer spicatum). There are ferns, mosses, lichens, and liverworts on the rock faces.
The creek bed is constantly changing. Where rocks and gravel have temporarily stabilized, tree species typical of floodplains - sycamore (Platanus occidentalis), cottonwood (Populus deltoides), and box elder (Acer negundo) - have taken hold. Impacts of human activities on this narrow greenway are extreme. Invasive exotic species proliferate in the naturally disturbed conditions of the gorge. Many are ornamental plants that must have dropped from gardens above.
Cascadilla Gorge is constantly eroding, and rocks continue to fall from the cliff sides, especially when the water flow is high and during freeze-thaw cycles in early spring. Both small and very large rocks, and trees as well, may tumble into the gorge. Notice that many of the trees have a bend at the base. When soil on these steep slopes slides downhill, the trees may become tilted. Later they bend to become vertical again. Erosion and landslides are exacerbated by human activities such as construction and changes in drainage near the gorge edge.