No, I’m not talking about the Utah rock band that hit the music scene in 2008. I’m talking about tree leaves that are on their way to being, or already are, neon yellow in color. We refer to this as “chlorosis” which is the lack of chlorophyll, the pigment that gives leaves their green color and is necessary for trees to produce energy through photosynthesis. While it is true that some tree cultivars are meant to have yellow foliage, such as ‘Princeton Gold’ Norway Maple, this article is to discuss the trees that shouldn’t have yellow leaves and how we address this issue at Oak Bros Tree Care & Removal. We sample dozens upon dozens of client soils and leaf tissues every year to isolate why trees are turning yellow in order to develop an accurate management strategy.
Benjamin Franklin famously said, “an ounce of prevention is worth a pound of cure” which couldn’t be any more true as it relates to chlorotic trees. Tree selection and placement are the most important parts of this equation. Trees have specific requirements that include their growing environment (soil, water, sun/shade exposure, hardiness, etc) to function optimally, so when trees are planted outside of their ideal environment, we still start to see them perform poorly. The most obvious example of this is the planting of Pin Oak in urban, developed soils.
Pin Oak is a bottomlands species which prefers wet, acidic soil. However, this is not where Pin Oak is planted in our urban forest. Our urban soils perform poorly and set some trees, such as Pin Oak, up for failure before they can mature. With high clay content, compaction, low organic matter, and high alkalinity, our urban soils are a sure way to develop a chlorotic tree if species selection isn’t considered first.
Chlorotic Pin Oak
You may be asking yourself “what is a developed soil?”. In the context of this article, developed soils are a result of removing forest or farmland to develop infrastructure (housing, parking lot, business, etc). In most cases, the organic matter layer of soil is stripped from the site and the remaining soil is compacted and exposed to the elements. Without the organic layer, the soil will perform poorly and result in stressed trees. Getting a clear view of a tree’s growing environment is paramount for success and subsequent management.
For soils to perform well, organic matter should be at or above 4%. Ideally, organic matter levels should be between 5% and 7%. Our urban soils, unfortunately, don’t contain a lot of organic matter. When working with chlorotic trees, one of the first steps we take is to send soil samples from your property for lab analysis. This helps us make recommendations for how to approach chlorotic trees. Without this information, we will have to make guesses that don’t yield the results we are looking for. For us to obtain predictable results, we need to make an accurate diagnosis. Managing chlorotic trees has a lot of moving parts and, while it is mostly a soil issue, takes time to fully correct. Over the years, Oak Bros has developed a systematic approach to gathering information and managing chlorotic trees.
It’s not as easy as purchasing iron or manganese from your local garden center, applying it to your yard, and watering it in. For those minerals to be available, they must be in an available form. Our urban soils are very limiting in their ability to make minerals available to tree roots. Without soil analysis data to confirm the true issue, treating with minerals is often a futile process and a waste of time and money. When managing your trees, we gather A LOT of data for soil and tissue so that we can provide you with the best recommendation.
Client soil analysis for which we base chlorosis management decisions on. Note the high soil pH, low nitrate, and low organic matter
I wish I could tell you, but that’s why we’re so good at what we do. Like Ed’s Sauce from Good Burger, it’s a secret. Is it as easy as applying minerals and getting a green tree? That’s a loaded question. Too often do we take over properties that other tree care companies can’t get results on. As stated earlier, chlorosis has a lot of moving parts and everything is interconnected. Too much of one mineral may reduce the uptake of another mineral. If a soil is low in organic matter content, long-term results will be poor. If soil pH is too high, minerals may precipitate out and/or become unavailable to trees. If soil minerals are too low in content, trees will not have enough resources to grow optimally. This is why treating soil for mineral deficiencies requires a lot of information and is what sets Oak Bros apart from any other business in our area that treats trees.
Assuming there are no other issues with your tree, by obtaining soil and tissue analyses, Oak Bros can make your neon tree look normal again. Through the use of micro- and macro-injection systems as well as soil and root management, we can make drastic changes in the appearance and health of your trees. The results truly speak for themselves.
Treated (left) and untreated (right) Red Maples
Before chlorosis treatment (left), after chlorosis treatment (right)
Our true secret lies in the knowledge our Plant Health Care program possesses. We know what works and what doesn’t. If you’re tired of not getting the results you want on your chlorotic tree, it’s time to switch to the Bros!
Aaron Schulz
Plant Health Care Director
ISA Board Certified Master Arborist IL-9078B
