Question
QUESTION: We have a transplanted Red Maple tree that is about 20 feet high and about a 4 inch trunk.  It has been in our yard about 4 years. I don't know what kind of Red Maple it is but when it leafs out it is a dark burgundy red then as the summer progresses the leaves become green until the cooler weather begins then they return to the burgundy color again.  Any ideas why this is happening?  We are told its "sister" tree (the yard where it came from) remains red all summer.  We are in eastern PA. Thanks

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

Also, red leaf (and other types of) maples can turn green if not given enough sun

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.



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QUESTION: Thanks for the information.  I have not fed the tree anything since it was planted except compost last year, and it gets full sun most of the day.  What should I do to get rid of extra nitrogen if that is the problem?

Answer
There is not a really good way to reduce Nitrogen in the soil. Over time the Nitrogen will slowly reduce. Compost is high in N and I would not apply this for a while. Watering with 1 inch of water per week will speed up the reduction of N (place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop). Do not over water.
About all you can do is enjoy the different colors.