Trees have been planted in cities since the 18th century. As a landscape feature, trees are part of the urban design of many cities. The Arbor Day Foundation recognizes cities that have not only planted trees but have programs in place to care for trees. Hardy city trees, such as the London planetree, ginkgo biloba and the hawthorn need to withstand pollution and severe pruning.
The London planetree is a hybrid of the American sycamore and Oriental planetree. The tree grows to a height of 80 feet. Its bark is light brown and peels off in patches to reveal a yellowish-white underbark. The London planetree can withstand high levels of pollution, severe pruning efforts and poor soil, according to the "Field Guide to Trees of North America," by the National Wildlife Federation. The leaves are similar to maple leaves with three or five pointed lobes. In the fall, the leaves turn brownish yellow.
Fossil records place the ginkgo biloba, or maidenhair tree, during the time of the dinosaurs, according to "The Easy Tree Guide," by Keith Rushforth. The tree grows to a height of 130 feet. The bark is gray-brown on young trees, turning completely gray as the tree matures. The green fan-shaped leaves turn golden yellow in the fall. The tree is planted throughout cities because it is highly tolerant of pollution and is not susceptible to disease. The seeds from the female tree are used in herbal medicine.
The hawthorn tree, particularly "Paul's Scarlet Thorn," grows to a height of 30 feet. Hawthorn trees are tolerant of dry soils and industrial pollution, according to "The Illustrated Encyclopedia of Trees of the World," by Tony Russell, Catherine Cutler and Martin Walters. The bark is gray and smooth when young, but later becomes cracked. The hawthorn tree's dark green leaves are oval. The tree blooms with rose-like flowers in late spring and early summer, and bright red fruit appears in late summer into fall.