My new Master Gardener class has said that all pertinent (feeder) roots of any plant, including all trees, grow in only the top 8-10 inches of the soil and that all roots below those are only anchor roots with no reason to feed them. Some of us tried to disagree but they would not hear of it. We have many companies such as True Green and the such that take care of lawns for people, using chemicals (yuck), one they do, as part of their regular treatment, is "deep feed" using long rods to go 3 feet or more down in the soil. I do not like those companies but it impresses alot of the people around here.


Anyhow, any thoughts on the 8-10 inch thing?

This information surprised me - Did your teacher provide a source? I found a lot of information relating to the root architecture of trees that indicates otherwise online (white papers studies, etc.) and in books I have in my collection. I didn't find one single source to confirm it (or even make a quantitative differentiation between roots that serve the purposes of absorption, storage and stability). Most important to point out is the many variables that influence root architecture, namely species, soil conditions and environmental conditions. (It is generally accepted that great variability exists within the same species.) Given such variables it's hard to believe one could make such an absolute statement (even an incorrect one).

You might find this study interesting:

http://www.forestry.gov.uk/pdf/fcin078. ... cin078.pdf

It does astound me also as I would believe that different minerals and such could be found at different depths based on rates and affects of decomposition, water availability, soil compaction, etc., etc.

One difference from the Dallas area, though, is the fact that I live right on the coast, or just a few miles from it, and our soil is solid gooey gumbo (70-80% of the houses built around here have cracked foundations) but still I would believe that different benefits exist at different levels of soil.

Anyones guess is as good as mine.

I found the study mentioned supported what you were hearing in class. The majority of the root mass are in the upper layers of the soil. And it is in that mass where the majority of the feeder roots exist. This is the reason that over the years most companys have shifted to what we call a "Root Zone Fert" and not a "Deep Root Injection". I have always believed that deep fertilization created a "pool" of nutrients below the root zone that supplied the tree, this way you avoided the green spots in your lawn from a topical application. And especially with chemicals you were at risk of burning the plant. However with our shift to organics, we found that injecting closer to the root zone prevented any waste or dilution of the fertilizer. And therefore was much more efficeint and responsible. Anyway thats my vote. I have seen too many uprooted trees that appear to have very little in the way of roots deeper than 12"-18".

Steve's right. Just not enough air deeper than 12" for much life to be going on. The root feeding is associated with the biological activity. Sure, there is some nutrient gathering from deeper but it is a small percentage of the whole.

I am trying to sell each day as a whole but the closer it gets to the show I would consider individual tickets so keep an eye out.

Growing up in an undeveloped and largely unaltered part of the Cross Timbers, I've seen hundreds of native trees toppled over the decades naturally . . . and I'd side with your teacher. Roots are far more shallow and horizontal than people realize. Tap roots are for moisture, not nutrients. Deep injection is snake oil, in my humble opinion.