Pin Oaks

A popular shade tree throughout much of Missouri is the pin oak. These native plants may reach heights of up to 80 feet, and grow from one of the smallest acorns in the oak family. It prefers rich, moist soil, but is widely adapted to other sites as well.

The pin oak is one of the easier oaks to transplant, due to its relatively fibrous root system. This makes it a popular choice for homeowners. It’s attractive, pyramidal shape also makes it an excellent selection for landscape design. Fall colors also make this tree popular among homeowners. The leaves first turn a reddish green and then scarlet.

This tree grows rapidly. Healthy specimens may reach 20 feet in seven to eight years. This can provide a quick shade, compared to slower-growing varieties. Many trees bred for fast-growing shade production don’t live long. While the pin oak may not grow as fast as some of these trees, it can live a long time, up to several hundred years if the tree remains healthy.

One of the more common problems with pin oaks is their inability to tolerate alkaline soils. They prefer acid soils, with a pH between 5.0 and 6.5. If the pH is higher than that, they will develop yellow foliage and stunted growth. This condition is known as iron chlorosis.

Iron chlorosis is caused by the tree’s inability to absorb iron from the soil when pH is too high. The solution is to lower the soil pH, and with time, the problem will be corrected. Iron sulfate or elemental sulfur may be added to the soil around the tree, which will lower the pH. In addition, iron chelates may be used as a foliage spray. This method is short-lived, however, and does not cure the problem permanently. You will still need to treat the soil to lower its pH.

If you have a pin oak that you suspect may be suffering from iron chlorosis, I would recommend that you submit a soil test to University of Missouri Extension so that we can see what the pH level is. After the results of the test are back, we can make specific recommendations on how to lower the soil acidity and correct the tree’s problem.

University of Missouri Extension programs are open to all