PPDL Picture of the Week
March 22, 2021
Chlorosis of pine trees
Tom Creswell, Plant and Pest Diagnostic Lab Director, Purdue University
Pines in much of Indiana often struggle on our high pH
soils. Many species of pine require a pH around 5.2 to 6.0 but many soils in
Indiana are 7.0 or higher due the limestone bedrock underneath. When the pH is
this high, iron (Fe) and manganese (Mn) may be in in a form that is not
available to the tree, even though they are present in the soil so the nutrients
needed for healthy green growth in pines can’t be taken up. The result is stunting
and, more noticeably, a yellowing of the needles.
Pine chlorosis is often more prevalent, or more noticeable
in late winter/early spring. There are two possible reasons for this. First, soil
that is often saturated during this time due to rains or snow melt. In
saturated soils, there is not enough oxygen and the plant cannot take up the
nutrients that is needs for normal growth. Second, the plant is also preparing
to grow and new growth (while still not visible to the naked eye) may be taking
nutrients from the older needles. This is common in many species, especially
those that grow in “flushes” like pines do.
While you can work to correct soil pH problems using
suggestions in this
article in the Purdue Landscape Report, the simplest solution is to avoid it by making
sure that you plant species that are adapted to your soil conditions.