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Chlorosis 101: Drought-Stress or Nutrient Deficiency? 

Save your trees from iron deficiency by knowing the difference & what to do about it. 


iron deficiency – iron chlorosis treatment. Sick yellow leaves of apple tree.

Chlorosis is a nutrient deficiency found in plants and trees. This month marks the transition from summer to fall and the beginning of the Midwest’s beautiful tree transition to fall colored leaves. However, if you start to notice those fall colors coming too soon, it could be a concern! Early fall coloring, or leaf burn, is often a sign of this underlying plant health care issue that does not bode well for the long-term health of a tree. If left untreated, chlorosis can lead to the loss of one of your property’s biggest assets, its trees! Here we explore this all too common problem by examining its symptoms, cause, effect and remedy.


Symptoms of Chlorosis

Be on the lookout for yellow foliage on your trees this summer. While yellowing leaves are frequently the result of drought stress, nutrient deficiency may be another culprit. What distinguishes chlorosis is the venation of the leaves. That is to say, the interior veins on a chlorotic leaf will retain a darker green color in contrast to the surrounding leaf tissue, while drought-stressed leaves will typically turn entirely yellow. As chlorosis progresses leaves will transition from a nice, dark green, to neon green, and eventually to yellow. Through this process, the veins of the leaves will typically remain noticeably darker. Although many trees are susceptible to this condition, the most common trees that we see this on are pin oaks, river birch and red maples. 


What Causes Iron Chlorosis in Trees?

The short answer is that most chlorotic trees are trees growing at the very edge of their native range. Where these trees are native, this issue is rare. The long answer is a bit more technical. 

The two most common causes of chlorosis in the Midwest are iron and manganese deficiencies. These elements are micronutrients for trees. This means that trees do not require a large amount of these micronutrients, but if they do not have what little they need trees can exhibit the symptoms listed above. It has long been known that chlorosis is not directly related to an absence of these nutrients in the soil, rather these nutrients are inaccessible to the tree. 

Trees absorb their nutrients when they are dissolved in water and taken up through the root system. Elements become water-soluble at different pH levels. The pH of the soils in our region tend to be very basic—or alkaline. At this extreme of the pH spectrum, both iron and manganese become highly insoluble in water. So, in our area, these micronutrients are not readily taken up by our trees. 

Recent studies are also showing that chlorotic trees also have reduced root systems. It is interesting that these two issues coincide, but there doesn’t appear to be solid evidence yet of which one proceeds the other. Did chlorosis cause a reduced root system or vice-a-versa? The jury is still out.


The Effect of Nutrient Deficiencies on Trees

Whatever the cause, the effect should be the most concerning to a tree owner. If you can remember back to your high school biology class, it is the color of a tree’s foliage that enables a tree to photosynthesize and produce energy for itself. As this color deteriorates, the tree gradually loses the ability to produce food for itself. As this progresses the tree will slowly begin to decline and can eventually die. Luckily, this process can take several years and its resolution is rather quick and relatively affordable.


Treatment for Iron Chlorosis

The straightforward solution is to artificially provide the tree with the deficient nutrient. There are many resources online which will direct homeowners to apply deficient nutrients to the soil around the tree. These may work in regions of the country far removed from our own, but they are ineffective here. 

Recall that our soil pH renders these nutrients insoluble. While after the initial application these nutrients may be absorbable, the soil conditions will almost immediately begin to reduce their availability to the plant. 

The nutrient deficiency itself is best resolved with the injection of the nutrient directly into the tree. The only time I recommend attempting to amend the soil profile is for trees that are too young to inject. In this case, you will be utilizing an inefficient treatment, but avoiding the wounds caused by the injection process. This is important for a young tree. Larger trees can sustain and recover relatively easily from the injection process

Most trees that become chlorotic from a nutrient deficiency will need to be re-treated again at some point in the future. By helping to re-establish a healthy root system, you can extend the length of time between professional treatments. A healthy root system will be more suited to capture what nutrients do exist in a water-soluble state in the soil. Practically this can be done by ensuring that these trees remain properly watered through adverse weather conditions such as drought. 

In addition to this, I also recommend treating the chlorotic plant with a plant growth regulator—or PGR—at or near the time of treatment. PGRs are products that are designed to redirect a tree’s energy away from canopy development and into root production. The effects of this application generally last up to three years and can greatly benefit the tree’s overall health. I highly recommend this treatment being done in tandem with nutrient treatment. Until we know for sure in what order the deficiency in nutrients and roots came about, you may just be masking the symptoms by merely treating the nutrient problem. 


Save Your Chlorotic Trees and Treat Today!

Sometime this week, take a stroll around your own property and inspect your plant material. See if your own trees could benefit from these relatively small investments into one of your property’s biggest assets. Ideally, these treatments should be done while leaves are on the tree for the purpose of properly diagnosing the cause of a tree’s yellowed leaves. 

Like caring for your lawn, the Pros at Ryan Lawn & Tree know how to properly diagnose and treat your iron chlorosis with the right products. Many of the products readily available to homeowners are not effective on larger trees. There should be some sense of urgency to administer the treatment as a chlorotic tree will more rapidly decline as symptoms become worse and its internal food production and storage become strained. Call us today at 855.216.2293 or request an estimate online!

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