Pale Leaves - Sugar Maple

Asked September 10, 2019, 12:15 PM EDT

Hi! this sweet little sugar maple needs some help. The newer and older leaves show chlorosis starting in the spring time. The leaves are light green in the spring and some start to turn yellow in July and August. It grows slower than the sugar maple next to it. The other tree that grows better is a little greener but still shows the same signs. I'm wondering if this is iron, zinc, magnesium or something else? Can you tell by the pictures what might be a good treatment to help it be healthier? I have more photos if that's helpful. Really appreciate it! Christie

Arapahoe County Colorado

2 Responses

Your tree does show signs of iron chlorosis which is commonly due to an iron deficiency. Many environmental factors also create or contribute to iron deficiency. These factors need to be evaluated and alleviated to the extent possible. In many situations, attention to watering and soil conditions will satisfactorily correct minor iron chlorosis problems.

Calcareous Soils: Many Colorado soils are naturally high in lime (calcium carbonate and other calcium compounds) which raise the soil pH above 7.5. In these calcareous soils, iron chlorosis is common on susceptible plants.

Over-Watering: Iron chlorosis is a common generic symptom of over-watering. Overly wet or dry soils predispose plants to iron chlorosis. Iron chlorosis is more prevalent following wet springs.

Soil Compaction: Soil compaction and other conditions that limit soil air infiltration (like surface crusting and use of plastic mulch) predispose plants to iron chlorosis by limiting effective rooting area and soil oxygen levels.

Trunk-Girdling Roots: Iron chlorosis is a common early symptom of trunk girdling roots in trees. The primary cause of trunk girdling roots is planting trees too deep.

Soils along the Front Range in Colorado are generally alkaline. In alkaline soils, iron is present in a chemical form less usable by plants. Plants that have a high iron requirement or are less efficient at taking it up from soil, such as silver maple, red maple or certain oaks, often develop iron chlorosis. Many Colorado soils are naturally high in lime (calcium carbonate and other calcium compounds) which raise the soil pH above 7.5. In these calcareous soils, iron chlorosis is common on susceptible plants. Colorado soils are abundant in iron, as evidenced by the common “red rock” formations. In alkaline soils (pH above 7.0), iron is rapidly fixed through a chemical reaction into insoluble, solid forms that cannot be absorbed by plant roots. Such iron will be tied up indefinitely unless soil pH changes. Soil applications of iron alone are ineffective, as the applied iron will quickly be converted to these unavailable solid forms.

An iron additive may be added and the soil pH lowered with sulfur products. The first step in using iron additives is to know the soil pH and free-lime (calcium carbonate) content. These soil factors directly affect the success of any approach.

Determine soil pH by a soil test. http://www.soiltestinglab.colostate.edu/

Here is a fact sheet that will give you additional info on this problem and ways to minimize it - including making sure to not over water in the spring time and minimize soil compaction.
https://cmg.extension.colostate.edu/Gardennotes/223.pdf

Hi, thank you, really appreciate the information. :) Christie