It’s midsummer and your garden is in full bloom but you’re starting to notice the leaves on some of your shrubs and trees are starting to turn light green with dark green veining. Over time the leaves continue to turn even lighter, eventually turning yellow. As the sun beats down on your shrubs and trees, the foliage begins to scorch in the sun and crinkle. You notice shrubs that usually should be flowering don’t, and eventually your plants begins to die. So what is going on with your once beautiful garden tree or shrub? It’s called chlorosis. In this article I’ll explain how it happens, and what to do to amend it, so that you can continue enjoying your trees and shrubs at their best health.
What is Chlorosis and why it happens
Signs of chlorosis are fairly easy to spot. It begins with the leaves on your tree or shrub turning a lighter shade of green. As days progress a dark green veining can be seen on the foliage. As the dark green veining becomes more obvious, the light green shade continues to lighten, and begin to take on shades of yellow. The loss of color in foliage tissue is due to chlorophyll no longer being produced. Which in turn leaves the plant vulnerable to damage. One major place to start in finding the cause of the lack of chlorophyll production is to look at the soil.
What's going on in the soil
One of the first places to look when investigating the cause of your tree or shrubs chlorosis is your soil pH. This can be easily done, by purchasing a testing kit available at your local hardware store, or garden center. Soil pH is a very important factor in the plant having a sufficient quantity of nutrition available within the soil, or if they are present, the ability to even absorb the nutrients at all. Very alkaline soil (pH over 7.0) can cause certain elements such as iron to become insoluble. Because the formation of chlorophyll is depended on iron, if the soil is too alkaline, iron may be inhibited from absorption. Other elements are also important in ensuring the plant can absorb what it needs to remain healthy. These include magnesium and zinc. Deficiencies in these two elements will result in the same symptoms seen in iron deficiency. It’s not just a deficiency of elements within the soil that may cause chlorosis. It’s also an excess of elements such as zinc, magnesium, copper, calcium, or phosphorus that react with iron, inhibiting it’s absorption by the plant. Highly alkaline soil can be due to a number of causes, but in the Great Lakes region in particular, limestone is a large contributor to highly alkaline soil. And if you’re a midwest gardener and are dealing with chlorosis, then checking the alkalinity of your soil is going to be crucial in amending your chlorotic issue.
Other causes of Chlorosis
Although soil pH and nutrient availability is a major factor in contributing to chlorosis, plant health is another detail to consider. Plants suffering from poor drainage, compacted soil, and injured roots won’t be able to absorb what they need to perform their best. Implementing good gardening practices such as mulching and core aeration to allow for oxygen, water, and nutrients to get deep into the soil will improve the soil quality. Core aeration will also assist in fertilizers reaching the roots of your tree or shrub more effectively.
How to fix Chlorosis
A few things can be done to amend the chlorosis issue in your trees or shrubs. After taking a soil pH test, consider adding aluminum sulfate or sulfur. Although both are effective options aluminum sulfate will react with the soil quickly, and change the pH much faster than using sulfur. One way to tell if your tree or shrub is suffering from iron, or magnesium and zinc deficiency, is to see where the plants are showing symptoms. Younger leaves that are situated on the outside of the plant showing signs of chlorosis have an iron deficiency. Applying a liquid iron will provide quick uptake for your tree or shrub. If your tree or shrubs older leaves, particularly those on the inside of the plant are suffering from chlorosis, then it’s likely a magnesium and/or zinc deficiency. Add calcium magnesium carbonate if you suspect a magnesium deficiency. If you find that it’s a zinc deficiency after your soil test, then apply a foliar spray that contains zinc. Spraying your plant or adding liquid a secondary nutrient will result in a temporary fix. Amending the soil itself is an important part of your plants long-term health.
Final Tips
Although watering your plants deeply and on a consistent schedule is important in making sure they are well taken care of, it’s also watering that can potentially wash away a lot of the nutrients the plants need to remain healthy. Along with being a great means to diagnosing other issues, taking a soil pH will enable you to really know where your trees or shrubs need the most help.
Adding the amendments needed to correct the soil pH, or sufficiently supply the elements the trees or plants need will correct the chlorosis the plant is suffering from.
Gardening is an investment. It provides curb appeal, real estate appreciation, and an esthetic appeal that everyone in your neighborhood can enjoy. Not caring for your investment isn’t just money lost, it’s time, and effort lost as well.
Sources
Schuster, James. Chlorosis | Focus on Plant Problems | U of I Extension, web.extension.illinois.edu/focus/index.cfm?problem=chlorosis. Accessed 30 August 2021
Combs, Sherry. Reducing Soil PH-Wisconsin Horticulture, 2007| University of Wisconsin – Madison hort.extension.wisc.edu/articles/reducing-soil-ph/. Accessed 30 August 2021