I’d like to stay on the topic of trees from last week, but today, I’d like to address the fairly common issue in this area of when red oak leaves turn yellow.
If you have this happening in your yard, I feel your frustration. I’ve been forced to educate myself on this matter, so I’d like to share what I’ve learned.
Red oaks are used quite a bit in this area. They can be beautiful specimens, provide great shade and grow rather quickly.
When you notice the leaves on red oaks taking on a yellowish tint when the veins in the leaves still look green, your tree may have iron chlorosis.
You may even notice the edges of leaves turning brown with some premature leaf drop.
Most local soil has a fairly high pH, and certain red oaks are not able to absorb the iron they need from the soil to produce enough chlorophyll.
Why does this happen to some red oaks and not others? A few reasons. Girdling roots might cause it, poor soil conditions may play a factor, but a higher probability is that the tree you purchased is a hybridized red oak and cannot adjust to the higher pH in the soil. If a tree is grown in an area with a low pH and brought to this area, it may not be able to adjust.
So, what can be done for a red oak with chlorosis? Many arborists say the quickest and surest thing is to remove it.
If the tree cannot adjust to the local pH, amending the soil is temporary, so it becomes an on-going, rather expensive option.
If one chooses to treat the soil because removing the tree is not an option, then consulting a professional arborist is a wise first step. There are many, somewhat complicated ways to go about treating chlorosis and a professional can give you expert advice.
Darla Horner Menking is a Texas Master Gardner and Master Naturalist. Contact her at firstname.lastname@example.org.