Hello, our young pillar oak has been showing signs of leaf chlorosis for two seasons. I applied Aluminum sulfite last year with no visible improvement, and earlier this season I sprinkled two applications of chelated iron. Is there anything else I can do to help this tree? Thank you.
Thank you for contacting Toronto Master Gardeners. Chlorosis refers to the yellowing of leaves. Causes of this symptom include: nutrient deficiency, root damage, temperature extremes, herbicide misapplication, too much light, too little water or too much water, insect feeding, or disease pathogens. Pillar oaks are susceptible to iron chlorosis. Iron is necessary for the formation of chlorophyll, which is responsible for the green color in plants and is a source of plant food and energy. When the amount of iron available to plants is inadequate for normal growth, leaves become pale green, yellow or white, eventually brown and die. Iron chlorosis is associated with soils that have a pH higher than 7.0. You might consider having your soil tested to confirm the pH level. There are other treatments for iron chlorosis:
- The first involves treating the soil with equal parts sulfur and iron sulfate. The mixture is inserted in to holes drilled around under the canopy of the tree. The holes need to be two feet deep and about fifteen feet apart beginning three feet from the trunk. This treatment may last two to three years before reapplication is needed.
- Another option is to drill holes into the trunk and releasing a cartridge filled with an iron solution into the water transport system. This approach provides a longer result if it is done properly. You might consider hiring a certified arborist to provide this treatment. You can find a list of certified arborists through Landascape Ontario.
Good luck with your tree.