Care of Japanese Maples
July 16th, 2005
Many homeowners purchase a beautiful Japanese maple in spring only to bring in burnt and damaged leaves in summer, worried that their investment is about to part ways with their yard. In most cases, the tree isn’t dying – it’s just suffering from heat stress. What most people experience is summer heat stress due to infrequent (or lack of) water when the tree needs it, especially during a heat wave. In hot summer climates, Japanese Maples do prefer afternoon or filtered shade.
Most Japanese maples will burn a little on the leaf tips in the first year while acclimating to a sunny or hot location. But after a few years, they become acclimated and burn less and less each year. The reason maple leaves turn brown on the edges in summer is that the tree is unable to replenish the moisture the foliage loses through natural transpiration. As moisture leaves a plant, the tree draws moisture up from the ground to keep the cells in the leaves healthy and robust. If the tree has no moisture to draw from, the cells burst and die, which leads to the burning one sees on the leaf edges.
This condition can also be caused by salt burn from the use or overuse of strong chemical fertilizers containing high amounts of nitrogen, especially ammoniacal nitrogen as well as salt uptake in alkaline soils. The salts can accumulate on the leaf edge, causing burning of the leaf tissues resulting in brown edged leaves.
What Japanese maples do need is a consistently moist, well-drained environment and, preferably, the use of an organic fertilizer. The term “well-drained” is key because regular watering in a poorly drained area will lead to root-rot and, ultimately, death. So never plant a Japanese maple in a low spot or next to a downspout or gutter. The amount of watering it takes to maintain a consistently moist condition will vary with soil type and location but on average established Japanese maples should be checked for watering every 2-3 days. A newly planted maple may need water every day in the heat of the summer.
Another way to cut down on heat stress and leaf damage is to spray the tree with an anti-transpirant that coats the leaves to hold in moisture and reduce stress caused by temperature extremes and a dry environment. Cloud Cover has worked well in most cases.