It is a subtle change but one day you notice that the leaves on one of your shrubs (or maybe a tree) are turning yellowish and as far as you know yellow leaves are not natural to this plant–even in Fall. You look closer and see that the veins in the leaves are still green as you can see in this photo.
Well, what you are looking at is chlorosis, a kind of iron-deficiency in plants that inhibits the development of chlorophyll, the stuff that makes green plants green and keeps them alive and growing. It is most common in plants grown in alkaline soils with high pH.
The problem begins in the dirt, the soil in your garden. Even in hot dry desert-like gardens there is ample iron in the soil, but unfortunately plants can’t access it. The technical causes for the iron/soil problems read like a chemistry textbook so I will skip it, but advise you to take steps to reverse the condition before it gets worse. After all, you don’t want to lose an expensive plant or tree, especially to a plant problem that is curable.
What you need to do at this time of year is apply a foliar spray of iron chelate (pronounced “key-late”) to the leaves of your plant. It is available online and probably at a local big box gardening or hardware store for less than $15. It may take repeated applications of the spray to green up your shrub again.
But even a foliar spray is a temporary solution, effective for two or three months.
The next steps are to
- Test the pH of the soil around the plant with chlorosis using an inexpensive pH testing kit which you can easily find online. You may want to test other parts of your garden too. (In fact, you may want to check the pH every year!)
- Add chelated-iron fertilizer to the soil around the plant or tree IN SPRINGTIME (not Fall). This is a longer term solution than the foliar leaf spray.
- Dig in extra amounts of organic materials in the Fall and the Spring to balance the soil in your plant beds to a neutral 7 pH. If you can get it to 6.5, all the better. Plants love 6.5 pH! Keeping a high level of organic materials in and around the plants is a long term solution to chlorosis.
BTW, if you have a Fan Tex Ash tree the leaves on it will naturally turn yellow in Fall. It is one of the very few trees for hot dry gardens that has lovely Fall color. (Of course, there are the aspen trees that grow in the mountains around the deserts and also become golden in Fall.)
CLIMATE CHANGE UPDATE
In an abrupt about-face the Australians tossed out their Prime Minister who announced last week that keeping fuel prices low was more important than meeting Paris Accord climate change limits. Among the first things the new PM stated was that climate change came first–particularly in light of the severe drought that is impacting ranchers in New South Wales, outside of Sydney.
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