Question
It is august and the leaves on my crimson king maple are turning from red to green and dropping.My neighbor has the same tree and it looks fine. What might be going on? What can I do to correct the problem?

Answer
Japanese red Maple leaves turn from red to green when the intensity of light is decreased.

Red leaf maples can also turn green if given fertilizer high in nitrogen.

Do not add any fertilizer especially those with nitrogen.

Most if not all varieties of red leaf plants lose the red color if the leaves are in a shaded area. This causes the new upper most leaves to become very red and the leaves that are shaded by other leaves to become green. Once these trees are given more space the red color comes back.

As the Fall approaches the leaves will turn from green back to red.

With all the grafts and selections of red maple and Japanese maple leaf color has been known to change with the seasons. The drought will also effect the color. This sounds normal to me.

The red color comes from the presence of sugars stored in the leaves. Some maples produce and store more than others. The sugars are produced by photosynthesis during the day as sunlight is absorbed. The tree for normal respiration and metabolic functions uses the sugars. The rate of sugar production is a function of daylight hours and the rate of respiration is a function temperature. The red color is strongest in the spring when the sunlight hours are increasing and the temperatures are still cool. This results in high sugar production and low consumption. The longest days are in June, in the northern hemisphere. As the days get shorter in mid to late summer the production of sugar decreases and with higher temperatures the consumption of sugar increases. This results in a net loss of sugar and as a result the red color fades to green as the sugar is depleted.

Some cultivars produce more sugar or consume less and as a result hold on to the sugars and red color longer. A tree planted in shade produces less sugar yet consumes the same as one planted in sun resulting in a loss of the red color sooner in the summer. This also explains why the red color lasts longer in northern latitudes than in the southern areas. The hours of daylight are longer in the northern latitudes during the summer and usually the temperatures are lower resulting in the sugars remaining in the leaves later in the year. The same cultivar planted in the same conditions in Portland might hold the red color until late August while the one in Atlanta might 揵ronze out?in late July. The result of an hour more of daylight and nighttime lows of 62 degrees verses 75 degrees.