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Street or highway medians
Trees in strips of soil between opposing lands of multilane boulevards (highway medians) should be chosen according to the width of the median.
Trees that have a mature size considered too big for the medium often grow slowly due to
confinement of the root system. A poorly developed root system could also cause the tree to fall over as it becomes larger.
Roots on trees that are too big for the space could eventually break curbing if roots grow under the pavement. One exception to this rule-of-thumb appears to be palm trees, which have small-diameter roots that rarely disrupt curbing. They are often successful in smaller spaces.
Trees in medians should be tolerant of drought to account for increased air and soil temperature near pavement, even if they receive irrigation. Trees should be tolerant of salt if de-icing salt is regularly applied near the root zone.
Upright trees may be more appropriate than low-branching, multitrunked trees with drooping branches in instances where drivers need visibility.
Trees without these characteristics are often considered better suited for planting along streets and near parking lots, patios, and decks. Remember that no trees are completely "clean." All trees drop something during certain times of the year. Some are simply messier than others.
