Sweet Gum

1. Q. I have a sweetgum tree, 18 years old and 30 feet tall and has had dark green leaves up until about three years ago and now the tree has the following problems. The leaves on some of the larger branches are undersize and look stunted, other leaves on other parts of the tree are pale green with veins showing and some leaves have black tips on them. I have used ironite granules and liquid iron in the prescribed amounts applied on the ground and also applied into holes bored around the drip line. Still the tree refuses to return to a dark green, healthy looking state. I live in Plano, Texas, Collin County, and as I drive around town I see many sweetgum trees that have the same problem as mine and some of them are in the same yards as healthy sweetgums. Why would some trees be affected and some not and how can I get this tree back to its beautiful green self?

A: The sweetgum is well adapted to the eastern half of Texas, in soils ranging from acid to very slightly alkaline. It can be grown in other regions, but shows iron-deficiency yellowing in highly alkaline soils. It does best in deep, well-drained soils and trees growing on heavy clay soils, such as you have in your area, can be weakened by drought. The symptoms you describe of "undersized and stunted leaves", "leaves with black tips on them" and "yellowing" are all signs of root damage. Root damage can be caused by herbicide injury, environmental stress of drought and/or unsuitable soil (too alkaline). It is hard to imagine that some trees could have a different environment than others growing just yards away but microcliminates of soil, temperature and moisture can make all the difference in the world determining plant health and survival. The application of an iron product to an 18 year old, 30 foot tree is doing nothing but wasting your money. -- it would be like trying to sweeten the Atlantic Ocean with a teaspoon of sugar. You could try pruning the tree back by selectively removing the most damaged branches and fertilizing in the spring. If you do not see improvement, you will have to selectively remove those specimens not responding and replacing them with adapted tree species recommended for your area.

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