Question
I have several, mostly fairly old, I think, lilacs. One of these older ones this summer developed a leaf pattern that appears to be exhibited on all of the leaves: The individual leaves have become mostly yellow, with some green remaining at the center and spreding out some along the veins. It has the general appearance of disease or malnutrition -it's quite noticable. None of the other lilacs exhibits anything like this, although none of the older shrubs are in close proximity to it. The ones that are close by were planted this spring, so perhaps, if this is a disease, they wouldn't have had time to be affected. Can you offer any help with this? Thank you in advance, Amy Horvat

Answer
Hi there:Sounds like Iron chlorosis.  There is abundant iron in our soil.  However, if the pH is high (alkaline soil) it is unavailable to some of our plants.  In advanced stages of iron chlorosis, leaves turn yellow between green veins.  Chlorotic areas may then scorch and die back.  Without iron, the plants cannot manufacture chlorophyll, the green stuff of leaves.  Peaches, apples, raspberries, roses and many other plants are affected by this problem.   Iron chlorosis may be aggravated by heavy soils, over watering, and high levels of phosphorous in the soil.
Recommendation: First you need to get a soil sample. Take soil from several different places, mix it all together  than take 1 sample from that total mix to your testing place. Follow recommendations from the testing lab to amend the soil if needed.
In early spring (before leaf break) apply iron chelate near the plant roots.  If iron chlorosis persists during the summer, spray leaves with a liquid formulation of chelated iron, but never during the hot part of the day.  Follow all label directions.
There are several other possibilities but lets try this one 1st.
Hope this helps, Bill