significant botanical differences from pedunculate oak ("quercus robur") include the stalked leaves, and the stalkless (sessile) acorns from which one of its common names is derived. it occurs in upland areas over with higher rainfall and shallow, acidic, sandy soils. its specific epithet "petraea" means "of rocky places". "quercus robur", on the other hand, prefers deeper, richer soils at lower altitude. fertile hybrids with "quercus robur" named "quercus × rosacea" are found wherever the two parent species occur and share or are intermediate in characters between the parents.