Tuliptree Forest. Forest communities dominated by tuliptree (also called yellow poplar) are characteristic of some lowland and mid-elevation areas of Catoctin Mountain Park and Harpers Ferry National Historical Park. Tulip tree is not uncommon in all four parks but usually occurs as a secondary component of forests with several other species of trees present. Since tulip tree does not form ectomycorrhizal associations, the fruiting bodies of the macrofungi involved in these associations are lacking. However, wood-decay fungi are not uncommon on the dead wood from tuliptrees, and the fruiting bodies of morels are sometimes found on the forest floor during late April and very early May.