What's Wrong With My Japanese Maple?

Elizabeth Gardner
Twin Ponds Landscape
804-883-6765

Even though I’m a wholesale grower, I frequently receive calls from homeowners who are stymied about signs of distress in their Japanese Maples. Many garden centers carry these trees, as their retail appeal is quite strong. Staff at the retail outlet may give advice based on their knowledge of woody plants in general, but which could result in damage to Japanese Maples. For your edification, I will relate a recent conversation with one such homeowner.

Susie Q called one morning in August. She had planted her first Japanese Maple in mid-Spring. She was told to plant it in filtered light and thought she had found a perfect spot in her yard. The tree received shade in the morning and sun only from 2:00 P.M. on. Susie took special care to work manure into the planting hole on installation to give it a good start. In late May, she noticed that the edges of the leaves began to bleach out. She again applied fertilizer. During June, July and August, she watered in the afternoon with her garden hose. In early August, the leaves began to turn brown along the margins. She increased her watering by setting up a sprinkler to run on hot days. She added fertilizer to no avail. The leaves continued to curl and drop. Suspecting an insect problem, she applied Orthene, a general-purpose insecticide she had used for years around her garden. Rather than looking better, the tree looked much worse. She asked my opinion as to what had gone wrong.

First, I took Susie back to the selection of her planting site. Japanese Maples do prefer filtered light. Protection from the afternoon sun, though, is advisable. Many cultivars will adapt to even full sun with proper watering. When first removed from the protected environment of the nursery and placed in more sun, leaf scorch to some degree would be expected with any cultivar. Susie located the cultivar name, and we were able to establish that this particular cultivar should do well in the given site.

Unable to turn back the hands of time, I explained that amendments to planting holes were generally not recommended, but that, in the case of a Japanese Maple, her preparations may have negatively affected the tree. Japanese Maples use very little nitrogen. I usually advise gardeners to install their maples and, aside from making sure they receive the equivalent of an inch of rainfall a week, to leave them alone. Too much nitrogen can cause leaf scorch, as well as unnatural growth that may disguise the true characteristics of the cultivar. I next recommended that she discontinue overhead watering during the heat of the day. This practice also contributes to leaf scorch in Japanese Maples. The additional application of fertilizer during a heat wave could have created additional nitrogen release, which was not beneficial. Finally, I warned Susie against cavalier use of pesticides. She had seen no evidence of insect damage and chose chemical that will burn a maple in a heartbeat. I recommended that she seek the advice of a Certified Nurseryman or her local extension agent in the future.

With all of the don’ts out of the way, I asked her about the current condition of the tree. The cambium was still green and new buds were forming along most of the branches. Mother Nature had challenged this tree with drought and heat. Susie Q had inadvertently compounded these problems with her misguided attempts to remedy the situation. Japanese Maples, in addition to being quite beautiful, are strong, adaptable plants. The signs of new growth led me to give Susie a positive prognosis. With proper watering and a little elective pruning, the tree had a good chance for survival.          

If you grow or sell Japanese Maples, you are aware that there is not much cultural advice in print for the trade or the homeowner. The best source book for the industry and the consumer is Japanese Maples by J.D. Vertrees. Recommendations for successful application of pesticides remain almost entirely anecdotal as very few chemicals are tested and labeled for Japanese Maples. If in doubt, call a maple grower.

NOTE: Twin Ponds Landscape sales of Japanese maples are wholesale only.