Spring is coming! Unfortunately, this also means thousands of Wyoming residents will watch their well-cared-for trees wake up, and promptly turn yellow. The yellowing is the symptom of a condition common in Wyoming called iron chlorosis. You can refresh your memory from our previous article explaining chlorosis in detail here.
A Long History of Chlorosis Research
There are lots of treatment options available, but for larger trees, they can get expensive fast. I’ve tried several things but ultimately had the best luck treating the trunk of the tree directly. I originally heard about this technique from research the University of Wyoming did way back in 1942. The technique is largely overlooked today as a long-term option. I think this is largely because the iron chelates available at the time had limited results. Today, we have a lot better form of iron that the plants can take up more readily.
I decided to conduct the experiment again, but with a different chelated iron that performs a lot better with our soil and water chemistry. The iron that I used is called ethylenediamine-N,N′-bis(2-hydroxyphenylacetic acid) or EDDHA. I know it’s a mouthful. This form of iron is unique because it performs well in even the most caustic of soils. Even though the iron is implanted directly into the trunk, the high alkalinity still seems to affect the bio-availability. I suspect this is because the sap of the tree itself becomes alkaline and therefore blocks the iron uptake. We can wax philosophical on iron chelates in another article, time for me to get to the good stuff.
How to Treat Your Anemic Trees
Get your supplies in order. You need:
- EDDHA iron chelate
- Cordless drill
- 3/8 or 1/2 drill bit
- Small funnel
- Tree wound sealer
- Small paintbrush
- Dowel or pencil (some kind of prodding device)
- Chlorotic tree (start with your own)
Make Implant Holes
First, you need to make a hole for the chelate. It’s good to use 3/8” bit on trees smaller than six inches in diameter. Use the 1/2” bit on trees over six inches in diameter. Drill a hole as low as you can practically reach on the trunk of the tree. The hole should be about three inches deep and aimed down at an angle to keep the chelate from spilling out. Drill two holes for trees less than six inches in diameter. Drill one additional hole for every additional six inches in trunk diameter. The holes should be evenly spaced around the tree. Don’t worry, these wounds will heal fast and won’t cause any long-term damage to the tree.
Fill With Iron Chelate
Next, place your funnel into the new hole and fill it with the appropriate amount of iron chelate. Remember to use EDDHA. Use ¼ teaspoons for each inch of trunk diameter. For example, if the trunk is six inches, use 1-1/2 teaspoons of chelate. If it’s 24 inches in diameter, use 6 teaspoons of chelate. Divide the iron chelate out evenly for each hole. If the tree requires 1-1/2 teaspoons and has two holes, add ¾ teaspoons to each hole.
Now, tamp the powder into the hole, ensuring it’s at least ½” below the bark line when finished. Its important that your chelate is below the bark and into the thin, live part of the tree, called the cambium layer. It’s also good to be deep enough to get into in the sapwood, which is about the outer quarter of the trunk. Going deeper really doesn’t do any good, because the deeper part of the trunk, called the heartwood, doesn’t move nutrients around. Also note that the reason the implants are placed low on the tree is to ensure uniform results. If you were to place these implants up a foot or two on the trunk, the treatment would be striped. The tree would green up in a patch directly above the implant but nowhere else!
Seal Up The Wound
After filling the trunk with chelate, carefully wipe any excess powder from the outer part of the hole so the wound sealer can adhere properly.
Finally, paint the wound with tree wound sealant. This will keep moisture out and keep the chelate in. It will also help seal the wound so diseases and insects can’t get in.
These treatments should be done before sap flow in early spring. The application amounts given here are on the conservative side. If the tree is still anemic after the first year, apply again. It does take several weeks for the iron to do its thing so be patient. Since the tree responds slowly, don’t re-apply in the same season. After all, you don’t want to burn the tree with too much iron.
Chelate trunk implants can last up to five years, or more. Just evaluate the tree at the end of every summer. If it looks like the leaves are starting to yellow and look anemic in August, plan a treatment the following spring.