Mountain Ash Tree Fertilizer

Old 10-02-07, 05:10 PM
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Mountain Ash Tree Fertilizer

I have a good-sized mountain ash tree. I had it pruned a while ago and was told that it is a good idea to fertilize this type of tree on occasion. After doing a bunch of web searches, I haven't found concrete information about what type of fertilizer is recommended nor how to do it. At one point, a gardener I chatted with recommended that I get something called "liquid iron" (I think), dilute it with water according to the directions and then pour it around the outside edges of the tree canopy. Does that make sense? Is it a good time of the year to do this (I'm in Wisconsin and leaves are just about to drop). The ground around the base of the tree is grass.

Thanks in advance for any info, links, etc.!
Old 10-02-07, 09:45 PM
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Hi Newt,

The liquid iron your friend talked about is probably ironite and is meant to help with warding off ash yellows. The iron is supposed to help green up the tree. One problem with using iron is it can be difficult for the tree to absorb the iron if the pH of your soil is alkaline. The problem with doing that now is your tree is slowing down and will be dropping it's leaves. Fertilizing with iron or a fertilizer high in nitrogen, might be a waste or, could cause a flush of growth just when your tree is slowing down. Nitrogen or iron, if used in the fall is best done in September. If your tree is infected with ash yellows you should use a high nitrogen fertilizer and the treatments I mentioned below and maintain vigor with proper watering when needed and proper mulching. Here's some helpful info from the Minnesota DNR about the three major ash diseases.

More info on ash yellows.

More info on iron and other trace elements.

If this were my tree, and it isn't showing signs of stress or disease, I would innoculate the soil with a mycorrhizal treatment and maybe a biostimulant using an soil auger.

Do a google search with: fertilize ash tree

Maintain the health of your tree with proper mulching and watering. Remove the grass under the tree. You might find these sites helpful.


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