Written by John Sepulveda, Certified Arborist WI-1454A
Chlorosis is a nutritional disorder in trees that results from a lack of micronutrients in the soil, poor root health or high pH in the soil. Chlorosis causes a lack of chlorophyll, the green pigment in leaves and the primary driver of photosynthesis. Hot, dry weather doesn’t cause chlorosis, but it can intensify the condition in trees that are stressed or suffered root damage in a prior year due to drought.
Chlorosis and Soil pH
Chlorosis does not mean that the soil is not fertile. Chlorosis is often caused by the inability of the roots to absorb nutrients due to high pH. Iron is most readily available when the soil is between a pH of 5.0 and 7.3. Above this, the iron becomes insoluble - unable to be dissolved in water - and thus becomes unavailable to the plant. This issue is very common in the southern and eastern parts of Wisconsin and can be seen in native trees such as oaks, red maples, white pines, and birches. It can also be seen in transplant trees like sweetgum, tulip tree and magnolia.
Signs of Chlorosis
The signs of chlorosis are yellowing of leaves, except for the veins which remain green. Chlorosis rarely will kill a tree and can be treated once the cause is determined. In some instances, not all of the tree will be chlorotic. Parts of the tree may be perfectly fine while only a small section is stressed.
Treatment can take the form of remedial nutrient applications or root condition repair. This is done by having the soil tested for nutrient content and pH level to determine the cause of chlorosis. From there, a plant health care technician can apply the proper treatment. Without a soil test it can be difficult to identify the cause of the chlorosis and money can be wasted treating the wrong thing. With compacted soils it is recommended to have soil aerated or tilling performed to create better soil characteristics for the roots.
If you notice leaves on your trees turning yellow, give us a call at 414.257.2111. One of our certified arborists can schedule an inspection to diagnose the problem and recommend a treatment plan.