Is it normal for this maple tree to have yellow leaves in late July? If not what is the problem and how might it be addressed?
Thanks for contacting the Toronto Master Gardeners. You ask if it is ‘normal’ for your maple tree to have yellow leaves in late July.
While it might not be ‘normal’ for leaves to become yellow in mid-summer, it’s most likely that weather conditions this summer have played a role. The yellowing of the leaves is a form of chlorosis. It can be caused by extreme fluctuations in temperatures compounded by long periods of minimal or no rain–all of which we experienced for a period of time this summer.
Nevertheless, the yellowing is actually due to a lack of uptake of manganese and/or iron in alkaline soil, predominant in the Toronto area. Even though these micro-nutrients may be present in the soil, the tree is unable to absorb them. One recommendation suggests that if the yellowing is not interveinal (where veins of the leaves remain green), one might add some nitrogen (fertilizer) to the soil [e.g. composted manure or fertilizer with high (N) nitrogen]. See here.
Without getting too technical, you might consider using an appropriate fertilizer or mulch to allow the tree to take up the nitrogen; in the future, if we experience more drought, the tree should not develop so much yellowing on its leaves. In the meantime, the yellowing is not a serious problem and has been caused by dry weather conditions.
July 27, 2021