Why are the leaves on my dogwood tree turning yellow?
If your dogwood’s leaves are yellowing faster than the trees around it, or during a time of year that they normally wouldn’t, the likely culprit is a condition known as Chlorosis.
What Causes Chlorosis?
Caused by an iron deficiency, chlorosis is the result of your trees inability to absorb enough iron from the soil, making it difficult for it to produce chlorophyll. Chlorophyll is the chemical that gives the leaf its green appearance.
There are several reasons chlorosis may occur. If the soil in which your tree is planted in is too alkaline (having a PH above 7.5) then it will be unable to absorb enough iron.
Reversing Chlorosis in Dogwoods
Soil PH can be lowered by adding organic matter like compost and mulches containing pine needles. Using fertilizers containing chemicals such as aluminum sulfate, sulfur, and sulfur-coated urea can also be effective.
It is important to note here that soil low in the minerals magnesium, manganese, and boron can also result in yellowing of leaves in dogwood trees.
Additionally, damage to the tree’s roots could impact its ability to properly absorb minerals, as can over-watering and/or poor drainage which can cause roots to rot. To determine if your soil has poor drainage you can perform the following simple experiment:.
- Dig a hole near the tree in question that is one foot deep and one foot wide.
- Allow the hole to completely dry out. This may take several days.
- Fill the hole with water and keep track of how long it takes to completely drain.
Ideally, it should take between 30 minutes up to 4 hours. Anything less and the soil is too dry. Anything more, the soil is too moist which can cause the aforementioned root rot.
Other causes of foliage discoloration
Other causes of discoloration of foliage include fungal infections like Crown Canker Disease, as well as insect infestations (i.e. Scales, Dogwood Borer). There are many factors involved in diagnosing and treating these conditions which is why it is recommended that you contact a certified tree expert to assist you in improving the health of your dogwood tree.