Problems with maple trees

Question: I have several maple trees.  Two of them are a very pale green (almost yellow) despite fertilizing.  Is this an iron deficiency or magnesium deficiency?  See pictures

responder: Travis County Master Gardeners  Replied May 08, 2023, 2:55 PM EDT
response: Yes, that is severe chlorosis, very likely an indication of iron deficiency, but there could be more going on, so it's hard to say for certain.  I'm not sure what variety of Maple you're growing, this link discusses some native varieties that can be grown in our area: https://www.wildflower.org/expert/show.php?id=378  It's not that you don't have iron available in the soil, but rather that the uptake is inhibited due to the alkalinity of the soil. This link shows a chart of how soil pH affects nutrient uptake: https://planetpermaculture.wordpress.com/2013/07/25/ph-chart-showing-nutrient-availability/  Instead of adding more fertilizer, you may need to use a liquid iron chelator. Chelators attach to the iron and allow it to be soluble in water. So be sure to water thoroughly with each application, and as always, follow the instructions on the label.  More tips for improving your tree's health:  1. Remove the grass around the tree, at least as far as the edge of the canopy and apply a layer (3" thick) of compost with another 3" layer of shredded hardwood mulch on top of that. Water the compost layer well to help activate the biological life.  2. Get a soil test done so you have specific recommendations for soil modification. For example, sometimes the phosphorous levels are naturally high and this can block the absorption of other nutrients. So if this describes your soil and you've been adding a fertilizer that contains phosphorous, then you could accidentally be causing a nutrient deficiency. We can't know without a soil test. http://soiltesting.tamu.edu/files/urbansoil.pdf  Hope this helps, Brittany Taylor

responder: The Question Asker Replied May 09, 2023, 2:05 PM EDT
response: Thanks so much for getting back to me so quickly.  I planted 5 maple trees that were of the same variety.  The property is along the Colorado River and has been used for sand and gravel operations in the past so much of the soil has been disturbed and moved around.  Two of the trees got iron chlorosis so badly that they died.  Two are light green/yellow like the picture I sent, but still growing and alive, and the 5th one (planted on one end of the line of trees) is normal green and thriving.  I'll get soil tests from the soil around the affected trees and around the healthy tree and see if I can come up with the answer.  I have been using 20-10-10 fertilizer but will go back to 21-0-0 for now and try the chelated iron.  I suspect there is plenty of iron in the soil but the alkalinity has prevented it from being taken up by the trees.  I guess there is no way to really acidify the soil to help with the situation, is there? Ken YoderOn Mon, May 8, 2023 at 1:55 PM Ask Extension <<personal data hidden>> wrote:

responder: Travis County Master Gardeners  Replied May 09, 2023, 6:33 PM EDT
response: Hi Ken,   You can certainly add "acidifiers" to your soil around your Maples. One of the best ways is to add mulch and pine needles around the base of the trees. The pine needles break down slowly, acidifying the soil.   However, I would not do too much until you get the results of your soil test, which will give you a better idea of your soil's pH.   Liz S.       Travis County Master Gardeners   Buy our Award-Winning Publications! "Garden Guide for Austin and Vicinity": https://www.tcmastergardeners.org/garden-guide/ "From Drought to Deluge: The Resilient Central Texas Garden" https://www.tcmastergardeners.org/drought-guide/    For live support, call our help desk at <personal data hidden> (leave a message)            From: ask=<personal data hidden> <ask=<personal data hidden>> on behalf of Ask Extension <<personal data hidden>> Sent: Tuesday, May 9, 2023 1:05 PM To: Travis County Master Gardener <<personal data hidden>> Subject: New response added to your question (#0098728)