Platanus
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The genus Platanus is a small genus of six species of trees native to the Northern Hemisphere. They are the sole members of the family Platanaceae. They are all large trees to 30-40 m tall, deciduous (except for P. kerrii), and are mostly found in riparian or other wetland habitats in the wild, though proving drought tolerant in cultivation away from streams.
They are known as planes in the Old World, and as sycamores in North America. Elsewhere, the name "sycamore" refers to either the fig Ficus sycomorus (the species originally so named), or the Sycamore Maple, Acer pseudoplatanus.
- Platanus kerrii or Kerr's Plane is a somewhat anomalous species, native to Southeast Asia, and differs from the other species in being evergreen, having unlobed leaves, and in the leaf stem not enclosing the axillary bud at its base.
- Platanus mexicana or Mexican Plane is found in northeastern and central Mexico.
- Platanus orientalis is the Oriental Plane, of southeast Europe and southwest Asia.
- Platanus occidentalis is the American Sycamore, American plane or Buttonwood is native to eastern North America.
- Platanus racemosa or California Sycamore is found in California.
- Platanus wrightii or Arizona Sycamore is found in Arizona, New Mexico, and northwestern Mexico.
- The hybrid Platanus x hispanica (P. occidentalis x P. orientalis; a.k.a. P. x acerifolia) is the London Plane, commonly planted in parks and along streets in most cities with warmer temperate climates. Having proved its city-tolerance in London's 19th-century industrial coal smoke, ironically it may be less tolerant of traffic fumes.
The seeds of the trees are borne in balls. Typically, the core of the ball is 1 cm in diameter and is covered with a net of mesh 1 mm, which can be peeled off. The ball is 3 cm in diameter and contains several hundred seeds, each of which is conical, with the point attached to the net, and has many thin stiff yellow-green fibers attached to the point.
Planes are susceptible to Plane Anthracnose Apiognomonia veneta, a fungal disease that can defoliate the trees in some years. The worst infections are associated with cold, wet spring weather. P. occidentalis and the other American species are the most susceptible, with P. orientalis the most resistant. The hybrid London Plane is intermediate in resistance.
Under the Cronquist system, Platanus was placed in the order Hamamelidales. Newer systems place it in the order Proteales.