A native of Europe, the Norway maple has been cultivated in the United States since 1756. Well adapted to North America, it is now considered an invasive species in parts of the Northwest and eastern U.S., capable of choking out other native trees. Hardy to USDA zones 3 to 7, the Crimson King (Acer platanoides 'Crimson King') with its reddish-purple foliage has particular horticultural appeal.
Featuring a moderate grow rate to an eventual height and spread of about 40 feet, the Norway maple is commonly seen as a street tree. Crimson King is a deciduous spreading tree with a dense symmetrical canopy. The branches tend to grow upright, without drooping, adding to its appeal as a parking lot specimen. The shallow roots, however, tend to eventually damage sidewalks if the tree is not planted at least 6 feet away from them.
Foliage and Flowering
Crimson King is most noted for its 4- to 8-inch reddish-purple lobed leaves borne in spring and summer. The foliage changes to a deep yellow or orange in fall. Shortly after leaves emerge in spring, tiny yellow flowers fill the tree. The flower tips have a red tinge, causing them to appear maroon. The 1- to 3-inch winged fruits aren't particularly showy, but do attract birds.
Planting and Care
Chose a planting location with full or part sun. The Crimson King can tolerate most soil types, but the roots may be stunted in poorly drained areas. It's best to plant the top of the root ball several inches above the existing ground level. Give the Crimson King plenty of water during the first year. Once established, it can withstand occasional periods of drought. Prune the tree in its early years to ensure a strong main leader dominates the canopy.
A few insects are known to attack the Crimson King, though none generally affect the tree's long-term health. Aphids suck juices from leaves and small stems, and secrete a clear sticky solution. The "honeydew" builds up on lower leaves and drips on objects such as vehicles below. You can treat aphids with insecticide sprays, but the bugs are a favorite food of many other insects and that tends to keep tree damage under control.
The cottony maple scale pest feeds on the undersides of leaves, creating a white film. Spray horticultural oils in early spring to control crawling insects before they begin to feed. Following periods of drought or other tree stress, boring insects may attack the Crimson King trunk. Insecticidal drenches applied to the root system are the best control. Follow label instructions.
Stresses may cause leaf tips to appear burned. There is no long-term affect, and trees should recover with adequate water. Verticillium wilt affects a wide variety of tree species. Crimson King Norway maple is no exception. Branches of infected trees wilt and eventually die. Prune out dead branches and look at the inner wood. Brown staining or streaks are a sign of the verticillium fungus, for which there is no cure. Fertilize trees with early signs of infection, because healthy trees can fight off the disease.