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Treatment options large silver maple for iron chlorosis #947225

Asked October 16, 2026, 9:06 PM EDT

Question: What is current best practice for home gardener wishing to treat a large silver maple for iron chlorosis? Background: I have a large silver maple that suffers from iron chlorosis. In June 2022 I had soil under tree tested at U of MN; pH level 7.9. ; recommendation included application of fertilizer with ratio of 7-10-5 which I did until this year when I started using recommendation from new soil test (pH 7.4) and fertilizer recommendation of 4-3-0. In fall of 2022 I applied a 50/50 mix of granular iron sulfate and elemental sulfur in holes in concentric circles from 3’ from trunk to around the drip line follow directions from Kansas State Extension Service https://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/Iron%20Chlorosis%20of%20Trees.pdf The tree improved over the next years. This year there are sections that are again showing yellow leaves with green veins. I wanted to apply the same granular mixture, but am having difficulty finding iron sulfate and elemental sulfur that I was able to purchase at Fleet Farm in Brooklyn Park in 2022 in about 25 lb bags. I cannot find granular iron sulfate in the larger bags and have only seen the elemental sulfur online at Tractor Supply in Greenfield, MN. There are some iron supplements in small bags, such as Hi Yield Iron Sulfate by VPG, which labeling states FE 20% and sulfur 11%. Are these an expensive alternative to what I used previously mixing the iron sulfate and elemental sulfur in equal ratio? Because my tree is large (20+in. diameter) it was recommended to apply 40-50 lbs of the mixture in holes around the area, which is a lot of 4 pound bags of Hi Yield. So, I restate my question. What is current best practice for home gardener to treat the above described tree? And, if I should use a product like the Hi Yield mentioned above, would I spread it as indicated on package directions on top of lawn and water in, or should I again use a series of holes in concentric circles around the tree and pour recommended amount of product in holes to get it to root level faster? Thank you for any suggestion or information you can share. Linda Chamberlain 5115 Balsam Ln N Plymouth, MN 55442 <personal data hidden>

Hennepin County Minnesota

Expert Response

Linda,

For home gardeners, the method you described w/ iron sulfate or elemental sulfur is probably the least expensive option. NDSU Extension has a great roundup about all of these methods, including what you have done so far.

The difference in drilling holes vs. surface application may depend on the amount of turf grass cover. The more turf, the more drilling/filling might be better. The one concern I have is when drilling holes is that you could accidentally damage roots. If the ground is bare, then surface application of the Hi-Yield iron sulfate might be OK.

You do have other options aside from iron sulfate or elemental sulfur. One product that is more expensive but is less impacted by your soil's high alkaline content is something called iron chelate. The amount you would need would be much less than elemental sulfur or iron sulfate, and the tree response could be pretty quick. Based on your soil pH, the type you would need to use is something called EDDHA iron chelate, other types might not work as well. You would apply this every year, and it comes in liquid or solid forms.

There are also products available to homeowners that can be used to directly inject iron into the tree, but these can be hard to find and can be difficult to learn how to do effectively. Lastly a tree professional can be hired to do this injection, but that could also be pricey.

Best,

Shane

An Ask Extension Expert Replied October 18, 2026, 11:06 AM EDT

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