Peter's Woods is on the sandy, north-facing slope of the Oak Ridges Moraine. Steep-sided valleys have been cut into this northern slope by surface runoff, springs and the headwater streams of Mill Creek. Deciduous forests of sugar maple beech, red oak and deciduous-evergreen forest containing hemlock and white pine dominate the slopes and well-drained uplands. Poorly drained wetlands support forests of white cedar, with local concentrations of red ash, white birch and other trees. The nature reserve also includes areas of land that has been used for agriculture. Peter's Woods has minimal facilities including a parking lot, trail and vault privies. Visitors are requested to stay on the foot trails to prevent trampling the vegetation and compacting the soil. The unauthorized collection of natural objects in the park is prohibited. Anyone wishing to conduct research must obtain an approved research application.