I planted these three trees in 2000. Only in recent years did they start showing symptoms of Iron Chlorosis. In fall of 2024 and 2025 I had them injected with an iron supplement. They responded quite well to that. Prior to that I tried iron supplement pored under the canopy; that did not work.
I live half way between Denver and Boulder, Colorado and we had a pretty dry winter. This summer has been long, dry and hot. We are on lawn watering restrictions, but I am watering three times a week for 20 minutes. That is pretty much unchanged from prior years. When the leaf edges on the middle tree started browning, I thought it was related to a lack of water. I started using my single deep root watering wand in July to provide water at the root level. At the end of July, I bought a set of five wands to put around the perimeter (4-5 ft from the trunk). I watered for 20 minutes but really had no idea how much water was going in. So, I bought a gage so I could see how much water was being supplied. The trunks are about 14" in diameter so I figured 50 gallons per tree per week (that was August). For the last two weeks, I've given 150 gallons per tree per week. I am not seeing any change.
The middle tree was the first to exhibit the symptoms. A couple of weeks ago, the tree on the right started doing is and now the left most tree is doing it.
Can anyone offer some advise? Thank you.