Botanical family: Platanaceae - Sycamore (1) Botanical name: Platanus x acerifolia ‘Morton Circle’ (1) Common names: Exclamation! London Planetree; London Planetree; Hybrid Planetree (1)
Photo from: Chicagoland Grows
Origin: Exclamation! is a selection from the interspecific hybrid of P. orientalis and P. occidentalis. The cross was made at the Morton Arboretum in Illinois, in hopes of creating an anthracnose-resistant, attractive tree (2).
Native Range: Exclamation! has no native range. P. occidentalis, however, can be found in southeastern US bottomland deciduous forests (3). The second parent, P. orientalis, is native to Eurasia.
Max. height: ~ 60 ft. (2)
Canopy spread: ~ 45 ft. (2)
Life Expectancy: This tree may live upwards of 100 years, and appears to thrive even in an urban environment (1).
Wood: Diffuse porous. Common uses include veneer, plywood, trim, pallets, flooring, furniture, and carvings (4).
Photo from: www.wood-database.com
Site Characteristics: Exclamation! prefers well-drained, generally moist soils with direct sunlight and air circulation. The tree can tolerate many different levels of soil pH, salt exposure, and drought. It is not tolerant of shaded sites. Best places to plant are south-facing sites that receive at least 6 hours sunlight per day. Site modification could include thinning surrounding vegetation to let in more light and air. Exclamation! is cold-hardy up to Zone 4 (2).
Reproduction: This tree is monoecious, meaning that there are separate male and female flowers on the same plant. The male flowers are green and inconspicuous, while the female flowers are more showy and red. Flowers appear in the spring, and tend to develop less when the tree is young. Fruits are densely clustered achenes which develop inside a ball-like hanging structure. Exclamation! is relatively easy to propagate from softwood cuttings – seeds will not be true to type (2, 5).
Uses: Exclamation! is an anthracnose-resistant urban plane tree which does well across a variety of site conditions. It has reportedly done well as a yard tree, boulevard tree, or even parking lot tree. The multicolored exfoliating bark is very attractive, and the large leaves provide for excellent shade in the summer and brief yellow autumn color. The seeds and flowers provide food for purple finches, goldfinches, insect pollinators, and squirrels. It would seem that Exclamation! might prove to be a valuable ash replacement in our urban settings (2, 5).
Maintenance: This is a generally easy tree to transplant near the beginning of a growing season. It does well in many site conditions. Pruning should be done in the winter so as to avoid infection from canker stain or infestation of wounds from American plum borer (6). Limitations: Exclamation! has good resistance to anthracnose. Canker stain is a disease which may affect this tree. Sycamore lacebug and American plum borer are insect pests of this tree. Additionally, it is often good practice to regularly fertilize and irrigate Exclamation! as it prefers rich, moist soils (2, 5, 6).
Brand, M. (2015). London Planetree. Plant Database – University of Connecticut. Webpage viewed Feb. 25, 2019.
Chicagoland Grows. Exclamation! London Planetree. Plant Introduction Program – Plant Release Bulletin, 24.
Sullivan, J. (1994). Platanus occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/tree/plaocc/all.html [2019, February 26].