Strolling the grounds of my one acre “estate” on a warm summer day, I was distressed to see something wrong with two of my Sycamore trees. While two of the trees looked great, nice dark green leaves everywhere, the other two had sections of leaves that had yellowed. Upon further inspection, I noted that the veins of the leaves were still green, but the areas between the veins had turned yellow. In some cases the edges of the leaves were brown. “What is wrong?” I wondered.
What was wrong with my trees was something called, Iron Chlorosis. This problem is apparently common in places that have high alkalinity soil (pH above 7.0). My soil was significantly above this level. It is believed that there is a link between alkalinity and iron in the soil. The problem isn’t a lack of iron, but the inability of the plant to benefit from the iron that is there. For some reason, chemical reactions render the iron unusable to the tree.
So, now that I know what is causing the trees’ problem, is there anything I can do about it? Yes, there are a number of things that can be done to deal with this problem. The best solution is prevention. Do a soil test to determine the soil pH and then select species that will do well in a particular soil. However, if the trees are already there, like mine, you have several options. One option is to add elemental Sulphur to the ground around the tree. The Sulphur will help free up iron for the tree to take up. This is a slow process and may take a year or more before seeing results. Another option is to inject iron directly into the trunk. This involves drilling a series of holes in the tree. This procedure should not be done more than once a year. Finally, the foliage can be sprayed with an iron solution. This usually provides the quickest results, however as new leaves come on they most likely will exhibit the problem. Solving the problem of iron chlorosis is a difficult and time consuming challenge. Research and careful planning and follow up are keys to your success. Saving all of your beautiful plantings are worth the effort.