Treating Chlorosis with Iron Injections

Posted by: Susan Rose, Tri River Area Extension

Grand Junction – Silver maples really struggle in our area.  I share a story with the Master Gardeners, that it wasn’t until I began volunteering at the Extension office that I learned that silver maples are actually supposed to be green – every one I had seen was yellow, so I thought it was normal for them!

While the best choice is to plant a more appropriate tree to begin with, there are still things we can advise the concerned homeowner.  Getting the watering right can go a long way.  The first challenge is to convince the client where the roots actually are.  Winter watering in this area is an absolute must for these struggling trees, as is avoiding excess water over the summer.  If you really want to guarantee chlorosis, ignore winter watering and run a drip daily in the summer, at the base of the tree!  Yes, we’ve seen this all too often.

A soil nutrient analysis would be very useful in determining what the plant actually needs.  Nitrogen is almost always needed as it gets leached out during irrigation, but in the case of the chlorotic maples we may want to consider the plant’s ability to take up iron as well.  In our high pH environment, the iron in our soils is not very available.

If a soil test confirms the need for additional iron, there are several options: soil applied, foliar, or injections.  Caution should be used and the overall health of the tree should be taken into consideration.  Which brings me to the story I want to share with you.

The tree above was injected with iron directly into the base of the tree.  The tree was under drought stress at the time of the injection.

Iron “burns” in a very distinctive way; the twigs and leaves turn a grayish black.

Note that the rest of the tree is now nicely green!

I don’t think the tree is a complete goner, but it will be a few years before it compensates sufficiently to look good again – by which time I suspect it will again be chlorotic.