Sycamore trees are also called American planetrees and buttonball trees. They got that name, buttonball trees, because of the spiky, itchy ball seed pods that they produce. In the spring these balls fall off the tree and break open letting the seed loose to create new sycamore trees and release pollen into the air to make people sneeze. Sycamore is not the most offensive of the spring tree pollens but it is still considered an allergen.