The green maple tree at right was turning yellow last summer and treated with EDDHA once at that time and once this spring. The light green maple at left was mostly yellow in early July, but with one treatment of EDDHA started turning green within one month.

Numerous large maples in the tree lawns in Stapleton are turning yellow and dying. Homeowners are responsible for replacement of these trees. It’s not only sad to lose big trees, it’s expensive and time-consuming to replace them. One homeowner appears to have found a solution that’s reasonably priced and takes minimal effort.

Untreated trees.

Help for Yellowing Maples

If you have noticed your maple trees turning yellow and it’s not yet fall, chances are that iron chlorosis, or lack of iron, is the culprit. Though Colorado soils tend to have sufficient iron, alkaline soils make it difficult for plants to absorb the iron, according to the Colorado State University (CSU) Extension office.

CSU’s Assistant County Director and Horticulture Agent Dan Goldhamer suggests testing the soil’s pH first, to determine which product will best work with your trees and soil. A soil pH over 7.5 and the presence of free lime might indicate use of an iron chelated with EDDHMA or EDDHA.

We found a Stapleton resident who, last summer, sprinkled a pound of Iron-EDDHA (purchased for about $30 on eBay) around a big maple tree that was starting to yellow. It got greener. With one treatment this spring, it now looks like a healthy tree. In July he treated a second tree that was almost fully yellowed. In one month it changed from yellow to light green. This is an ongoing experiment by someone who is not a botanist, but so far it appears to him that one treatment a year is enabling the tree to absorb enough iron to remain healthy. He had previously tried the cheaper and more accessible Iron-EDTA but found that it had no effect on the trees in the alkaline soil that predominates in Stapleton.

You can request a soil testing kit online, reach a Master Gardner and upload photos of problem trees at: https://cmg.extension.colostate.edu/ For more information, see: https://planttalk.colostate.edu/topics/weeds-cultural-problems/2121-iron-chlorosis-trees/