Bedrock and glacial till close to the surface of the acidic soil limit the availability of water and cause the wide spacing between the oaks. Likewise, the dry soil cannot support a tall shrub layer. When shrubs do occur they are usually limited to patches of mountain laurel and a covering of lowbush blueberry and huckleberry, both of which grow no taller than your knees. These heaths obtain moisture from the humus through their roots. With all those oaks Harriman Park is not a woods to visit in a gypsy moth-infestation year.
Small swamps pepper the hills of Harriman.
You may encounter a burn area anywhere in these woods but especially over deciduous crests and on the sides of summits where leaf litter had accumulated. At the intersection turn right onto the old woods road of the yellow-marked Dunning Trail. This same weighty glacier is the one that rounded this bedrock ground down the entire Hudson Valley landscape of gentled hills. Pine Swamp is one of a number of bogs in the area perched within a glaciated bedrock bowl that holds water. This sphagnum marsh is a great place for botany, pond life, birding, frogs, or just sitting by the open water on rocks gazing at the spatterdock and white water lilies.