Norwegian Maple, known botanically as Acer platanoides, is a species of deciduous tree with colorful fall foliage. As mid-size trees they reach roughly 20-feet in height with a canopy up to 20-feet in spread. Thriving in full sun or partial afternoon shade they are hardy to USDA Zone 4. Norwegian maple is not a species of tree known to be disease prone but can suffer from some common maladies found in the Acer genus.
Verticillium wilt causes the twigs and branches of Norwegian maple trees to wilt, become defoliated and die back. If the disease progresses and the tree cannot outgrow it, the disease will spread into the trunk sapwood blocking the flow of moisture and nutrients eventually killing the tree. While there is no cure for vertcillium wilt, generous watering and fertilizing of the tree along with light pruning and removal of infected wood and tissues will help the tree develop healthy wood to compensate for diseased and dying wood.
The leaves and tender branches of Norwegian maple can experience scorch when ambient temperatures are warm and winds are high. Maples undergoing drought, root rot or some other stress will experience more severe scorch damage than healthy, well hydrated trees. Scorch is evidenced by discolored or dead patches on leaves between the veining and brown splotches on tender green tissues of stems and new twigs and branches. Scorch can be prevented or its effects lessened by generous watering of the maple so that the soil is always moist to a depth of one-foot and the tree is never under drought stress. Surrounding your Norwegian maples with larger trees to provide some shade protection in very warm climates or a windbreak in perennially windy sites can help to protect the trees from scorch.
Norwegian maples are susceptible to chlorosis due to a lack of the trace mineral manganese in the soil. It can also be caused by the soil having too high a pH and making the tree unable to absorb the manganese that does exist in the soil. Manganese deficiency is evidenced by out of season yellowing of the leaves before fall, green veins but yellow or pallid green surrounding leaf tissue and limp foliage or slightly wilted foliage. This can also be caused by iron soil deficiency but manganese uptake is much more common to Norwegian maples. Amending the soil with manganese nutrient tablets will correct the deficiency. If overly alkaline soil is the problem a soil test and acidifying soil amendments applied in the indicated amounts will correct the ability of the maple to uptake the manganese.