Chartreuse isn’t the first color we think of to describe tree leaves. The color is half green/ half yellow, but it is the perfect color to describe many trees in the area right now. What is causing trees to be this color and why is it happening now? Chlorosis could be to blame and there are many causes for the yellow/green color. With a little know-how you can have your trees back to their dark green color.

Chlorosis describes any condition in which leaves or needles develop an abnormally light green or yellow color. Symptoms of iron chlorosis include yellow or pale green leaves with darker green vens. If severe enough, it can leave to scorch or browning along the leave edge or along the veins and branch dieback. If the tree is severely affected, it can lead to decline and death of the tree.

There are many causes of chlorosis, but the most common reason for chartreuse leaves in our portion of the state is due to iron chlorosis. Iron chlorosis is caused by an iron deficiency in the tree. It causes the trees to turn an off light green/ yellow color. Often the high pH of our soil makes iron unavailable to the tree. We have iron in the soil, but it is difficult for the tree to absorb it. Other factors that can cause chlorosis include wet and/or compacted soils, root damage, high nitrogen or phosphate levels, or low levels of other micronutrients like manganese.

Some trees are more affected by iron chlorosis than others. Trees that most commonly suffer from iron chlorosis include some species of maples like silver, red, and Freeman; pin oak, crabapple, pear, baldcypress, and birch. A few other trees can suffer from this deficiency, but sometimes they have underlying conditions that compound the severity of the deficiency.

There are several methods for treating chlorosis. The treatments depend on the size of the tree and each has their advantages and disadvantages. If you have a young tree with severe iron chlorosis it might be more cost effective and beneficial to select a replacement tree that isn’t susceptible to iron chlorosis. Applying a product like sulfur to the area around the tree can help to lower the pH of the soil and make the iron more available to the tree. This method is inexpensive, but its a slow method. To change the pH of the soil around the tree might take year or two before the improvements can be seen.

Combating iron chlorosis by applying iron chelate directly to the soil is another method. These products contain EDDHA (FeEDDHA) or ethylenediamine di-(o-hydroxyphenylacetate). These products are water soluble and can be dissolved into water and poured around the base of the tree. This method can be expensive and have short term effects, meaning more applications would need to be applied yearly to have an effect.

Other methods place the iron directly into the trunk of the tree. Trunk injections or iron implants can put the iron directly into the trunk of the tree by holes drilled in the root flare. These methods are effective and can last from 1-3 years. The disadvantages are that these methods create a wound in the tree each time it is treated. Over time the tree can become completely girdled and unable to take up moisture. Iron injections should be done by a certified pesticide applicator, which can add to the cost. The best time of year for treatments is either in the fall or in the spring of the year. Making applications right now in the heat of the summer isn’t a good idea. The tree might not take up the iron, and in some instances, it can scorch or burn the tree.

The Whitcomb Method places a grid of holes are drilled in the soil beneath the tree’s canopy and filled with three products- sulfur, a complete fertilizer, and a micronutrient fertilizer. This method can be very effective and provide long-term chlorosis control, but the initial treatment is labor intensive and it can be difficult to find the micronutrient products.Iron nails, shavings or other forms of solid iron buried in the soil or put directly into the tree are not effective in treating iron chlorosis and should be avoided.Don’t let chartreuse leaves get you down. With a little iron or some sulfur, you can have your trees in the full green glory before long.

Elizabeth Exstrom is the Horticulture Extension Educator with Nebraska Extension in Hall County. For more information contact Elizabeth at elizabeth.exstrom@unl.edu, her blog at https://huskerhort.com/, or HuskerHort on Facebook and Twitter