Whether you live in an area in which red oaks occur naturally or you wish to cultivate your own, red oaks can add beauty, function and shade to any area in which they are grown successfully. Like any other tree, however, red oaks are far from immune from diseases, insect interference, mold and fungal infections and other potential problems that can potentially threaten the health and life of your oak if not properly managed. Brown leaves can be an indication of any of a number of these problems, and identification of parallel symptoms will aid in a proper diagnosis.
Early Fall Colors
Leaves turning brown may not even necessarily be an indication of a health problem with your tree. Red oak leaves turn brown in the fall. If you have noticed the leaves turning brown, it is most likely because they have turned brown out of season. Note, though, that the onset of fall colors on red oak leaves depends on a near-limitless list of factors, including unseasonably warm or cold temperatures and shortening days. Leaves turning brown out of season could simply be a result of early onset of fall colors due to these natural factors.
Brown leaves may also be the telltale sign of a more serious problem with your oak such as iron chlorosis, a disease resulting from an iron deficiency in the soil. Leaves first turn a pale green or yellow color but with thin streaks of green along the leaf veins. Treat iron chlorosis with an iron-rich fertilizer or chelated iron. If applied carefully according to the manufacturer's directions, your red oak should return to normal growth within a season or two. Note, however, that if soil pH is too high, even supplementing iron in the soil may not correct the problem.
Both underwatering and, ironically, overwatering can cause leaves to turn brown and brittle. If your red oak did not receive sufficient moisture or suffered under unusually high temperatures, the tips may turn brown and dry. Overwatering can cause the same symptoms. The proper watering schedule for red oaks entirely depends on the amount of rainfall it receives, but in general, red oaks should be watered so that the soil around the roots is moist but not soggy. Adjust the watering schedule and see if your leaves return to their normal colors.
Brown leaves are one of the most common symptoms observed on trees in poor health, so there are many other possible diagnoses, including overfertilization, terminal chlorosis, insect interference, environmental stressors or fungal disease. If you are unable to make an accurate diagnosis on your own, university extension offices can often make on-site diagnoses for you.
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