Wanna Waste Money? Amend Your Soil

November 1, 2009 | By | Comments (6)

Autumn Blaze maple

 ‘Autumn Blaze’ maple at Bernheim Arboretum in Clermont, Kentucky

Dear Grumpy Gardener,

Why do I find some instructions saying when I plant my tree, I should not amend the soil with any compost, peat, other soil, or fertilizer? It says to  backfill with the soil that was removed from the hole. Other times I have read to mix the removed soil with all sorts of things to loosen it up. I have a bag of Tree and Shrub garden soil.

Do I or do I not use it to plant my beautiful 10 ft. Autumn Blaze maple? Jo

Grumpy says:

Here is why I don’t believe in amending the soil when planting a shade tree like ‘Autumn Blaze.’ Many people think that the root system of a tree is a mirror-image of its trunk and branches. It’s not. In fact, the root system of most trees looks pretty much like a pancake spreading far beyond the branches with the vast majority of roots in the top 6 inches of soil.

What’s this means is that the roots don’t stay in a tiny hole of amended soil. They spread out into the soil you have. Amending soil may actually inhibit root growth, as roots don’t like growing from one type of soil into another. So what you should do is this:

1. Dig a hole at least three times wider than the root ball, but no deeper
2. Plant the root ball so that its top inch rises above the soil surface
3. Backfill around the root ball with loosened soil you dug out
4. Water thoroughly to settle the soil
5. Cover the top of the root ball with mulch.

The tree probably comes with slow-release fertilizer added, so there’s no need to add more now. In the future, fertilize the tree by sprinkling tree fertilizer on the soil surface underneath the branches, but not up against the trunk.

Yet Another Reason I Resent My Son

Homecoming 010

This is my 15-year-old son, Brian, and his date for the Homecoming Dance, Savannah. I told him to make sure he picked a cute girl and he obviously followed instructions. So why am I resentful? Because I didn’t have a date until I was 38 years old. Oh sure, eventually I married a hottie, but there were 25 lost years in the meantime. What a tragic loss for all of femaledom!

COMMENTS

  1. Deirdre

    When I was in hort school, we were told that trees get most of their nutritional needs met by their own fallen leaves. Leave the leaves. Skip the fertilizer. In my garden, leaves that fall in the beds get left (unless there is a disease issue, but, then again, I wouldn’t plant any tree with disease issues like anthracnose.) Any leaves that fall on the grass get mowed with a mulching mower and left. Someday, I hope to get a leaf shredder. Then I’ll shred the leaves in the bed and put them back. Big leaf maple leaves take a LONG time to break down otherwise.

    November 1, 2009 at 12:01 pm
  2. Ilona

    Your son and his date are precious :) He looks like he got good genes – so you aren’t near as gruff as you make out;)
    I second Deirdre on how long maple leaves take to break down!
    Planted trees using both streams of advice. Prefer adding amendments because it seemed to give trees a bit of a boost at the beginning.

    November 12, 2009 at 7:47 am
  3. Grumpy Gardener (aka His Excellency)

    I think amending the soil may work at the beginning, because the people who do it are more likely to give the tree other kinds of care as well, like watering, mulching, etc. But what happens when the original amendment you added breaks down and isn’t replenished? Doesn’t the tree notice?

    November 13, 2009 at 2:51 pm
  4. tom | tall clover farm

    I’m in total agreement on the soil amendment issue; don’t bother. In my unofficial study, it seemed to provide no advantage. Initially maybe a growth spurt with the amended soil trees, but then within three years the other bare root trees with no soil amendment soared well above their pampered counterparts. One American Chestnut I planted as a twig turned into a mighty hulk with little more than regular watering and no soil tampering.
    And as for leaves, I just mulch and collect them with my rider mower and spread the contents as a wide ban around the trunk (but not touching) out several feet. My trees love that, or so it seems.

    December 17, 2009 at 6:38 pm
  5. Henry H.

    I can see where you guys have a point but please remember….
    Not all people have the same soil condition. We live in a very, very sandy area(St. Simons Island, GA)and people are frequently planting throughout the year. Now here is my point. When trees are planted in the summer here and elsewhere in these sandy conditions the water retention of a tree is paramount. By ammending the soil you are increasing these h2o retention properties thus aiding the tree in its new home. I would hardly say it was a waste of money but I also know that Gen. Oglethorpe was not out here ammending the soil for all these beautiful oaks and look at ‘em now!!!!!

    December 19, 2009 at 2:41 pm
  6. J

    I live in a part of California where the soil is basically all rocks just beneath the surface. These are not small rocks but big rocks that compact into concrete like soil. I have found that I get the best results by removing large diameters of soil and depth and putting in good soil. When I plant trees using this method i settle the soil with water and when I plant the tree I plant it high as the soil will settle further. The trees I have planted this way have well out performed those planted more traditionally as described here. Maybe it s wrong, but it has worked with these soil conditions.

    April 14, 2012 at 12:22 am