A yellow tree is a sick tree
Iron chlorosis is a serious and widespread problem across the Front Range and Fort Collins area. Typically the problem stems from our soil pH being too high, which reduces a plant's ability to absorb Iron through the roots. Only rarely is the actual Iron content too low.
Some trees and shrubs have a particularly hard time picking up Iron from alkaline soils, including:
- Autumn Blaze maples
- Other red maple/ silver maple crosses
- Silver maple
- Pin oak
- Ornamental pear
- Mugo pine
The symptoms of Iron deficiency are easy to see: foliage begins to turn pale green, then yellow, and in severe cases leaves can be almost white or translucent with scorching, and will drop off. At this point branch dieback begins. Since Iron is needed to produce chlorophyll, and chlorophyll produces the plant's energy, severe Iron deficiency weakens the plant and can lead to its demise.
Treating Iron Deficiency
Correcting an Iron deficiency, or chlorosis, is regarded as being difficult or even impossible. Last I heard, the Colorado Master Gardener class is teaching that it is not possible or practical to fix Iron chlorosis. Thankfully, that's not the case, as I've been able to fix hundreds of trees and shrubs.
Some are easier than others, with Autumn Blaze maples and Pin oak being the most difficult to turn around. Still, with the treatment I do, many respond extremely well after just one treatment while the most stubborn will still show improvement within about a year.
One of the techniques I use to correct Iron deficiency is to apply a special formulation of Iron to the soil. This is generally regarded as ineffective by most people and tree services, however, the photos below all show the results of just one soil-applied treatment. So obviously it can work. In my opinion it is the preferred way to fix a chlorotic tree and in almost every case should be the first choice.
Once a tree has greened up and looks healthy again, the Iron treatments can be put on pause until symptoms reappear, which may be years down the road.
So why do the treatments work when I do them but not when other people attempt it? I'm sorry but I'm not about to post the answer online!
For trees that do not respond to the soil-applied Iron treatment, it is possible they instead have a Manganese deficiency. The symptoms are identical. A foliage sample can be taken and tested to determine if a Manganese problem is the culprit. Maybe 1 in 10 chlorotic trees in our area have a Manganese deficiency.
When all else fails, or if the root system of the tree is compromised or obstructed, we can instead perform a trunk macro-injection of Iron and Manganese. The macro injection works better than the micro injections or capsule injection of years past.
Iron trunk injections should be done in September, and will typically last two years, especially on maples. After two years, the tree will have to be injected again or the effects wear off. This is one reason it is better to start with the soil treatment; the trunk injection has to be repeated for the life of the tree.