London planetree (Platanus x hispanica or Platanus x acerifolia) is reported to be a hybrid between the American sycamore (Platanus occidentalis) and the oriental plane tree (Platanus orientalis). The tree appeared in Europe before 1663 and has been widely planted in cities all over the world because it was perceived to have a tolerance for urban pollution. Compared to the sycamore, the London plane tree has fruiting balls clustered in pairs rather than hanging as a single ball. Further, the distinct exfoliating bark on London plane trees, which coloring looks like army camouflage outfits, occurs on the entire tree while on a sycamore it does not occur at lower levels. The London plane tree typically grows to 75 to 100 feet with horizontal branching. This is a fast growing tree – trees with 3’ thick trunks may take only 100 years – able to withstand urban pollution and annual pollarding (pruning). Its large 3-5 lobed leaves have coarse marginal teeth and turn brownish-yellow in the fall. The reddish female flowers give way to fuzzy, long-stalked, spherical fruiting balls that ripen to brown in October and persist on the tree into early winter. Each fruiting ball consists of numerous, densely-packed, tiny seed-like fruits (achenes). Besides its street and garden value the tree makes attractive golden brown wood, known in the trade as ‘lacewood’ used for veneer. There are many streets in Princeton, such as Hibben Road, where you can find rows of beautiful large London plane trees. The Hibben Road trees must be close to 100 years old.
Common name: London Plane Tree, Western Sycamore
Scientific Name (family and order): Platanus x hispanica Mill. ex Munchh. or Platanus x acerifolia (Aiton) Wildenow (pro.sp) (Platanaceae, Proteales)
Species Origin: hybrid discovered in Europe of P. occidentalis and P. orientalis
New Jersey Status: USDA Introduced
Habit: 70 – 130’ tall x 100’ wide; bole 2 -4’ diameter. Trunk straight, stout; broadly pyramidal to rounded crown.
Habitat: Zone 5 -8 .
Trunk/Stem: Bark brown, gray and creamy flaking in patches. The inner bark has greater yellow hue than that of P. orientalis and not as multicolore as P. occidentalis.
Leaves: Deciduous, alternate, simple. Leaves palmately shaped, 8“ long and 10” wide with three to five large shallowly divided, pointed lobes; glossy bright green above and paler beneath covered in scurfy brown hairs when young. Veins are palmate, meeting at the long petiole insert, are conspicuously yellow. Winter buds form inside the base of leaf stalks.
Flowers: Monoecious. Male and female flowers very small; male yellow, female reddish borne in separate, small round clusters on the same plant in late spring.
Fruits and seeds: Fruit a round dense cluster, 1” across, green ripening to brown covered in spiky brown bristles. Two fruits hang together; fruits persist on the tree during winter.