Should You Amend Your Soil?

April 3, 2014 | By | Comments (9)
Soil Amendments

Photo: MDgovpics

Planting time is finally here (except in Minnesota haaaaaaaaahh!!). So how many of you think it’s a good idea to amend your soil with peat moss and stuff before planting anything? It sounds right, so it has to be right. Right?

Not so fast, Grasshopper. Sometimes amending is good and sometimes it’s useless or harmful. It all depends on what you’re planting, how big it’ll get, and how many things you’re planting.

Amending the soil (especially with lots of organic matter, like peat, composted cow manure, chopped leaves, and kitchen compost) makes sense when what you’re planting has a relatively confined root system — like a flowering annuals and perennials, vegetables, herbs, and bulbs. It also makes sense if the plants need acid soil, like blueberry, azalea, or heath, and your soil is alkaline, or if you’re preparing to plant a new garden bed that will contain groups of the same kinds of plants.

On the Other Hand…
But what if you’re planting a crepe myrtle that will get 30 feet tall, an oak or maple that will get 60 feet tall, or a cherry that spreads 25 feet wide? Then it’s a different story, because the roots of these big plants will spread about as far as the branches. So you gotta ask yourself — how do I feel about digging a hole about 30 feet wide and amending all that soil? Am I totally loving the prospect?

Personally, I’d rather drink this here beer. (Of course, that’s my first option always.)

Soil Amendments

Photo: Stone Brewing

As a rule, don’t amend the soil when planting a tree or a shrub that gets big. Why? because most of its roots will grow beyond the hole where you added soil amendments. Instead, focus on getting the tree or shrub off to a good start by digging a hole that’s three times the width of the root ball — but no deeper. Place the root ball in the center of the hole and backfill around it with the original soil you just excavated. The roots will appreciate the loosened soil and quickly adapt to the soil type of the surrounding yard. Then water and add mulch over the top.

But, But, But……………..

Soil Amendments

Photo: storyvillegirl

“What should I do if I’m planting a tree or big shrub and my soil is nothing but crummy red clay, sand, gumbo, or rocks? My Mom said to add peat moss! You must want my tree to die, you big, mean Grump!”

No, I don’t. I want your tree to live! So if you find yourself in a desperate situation like this, look around at the native trees that planted themselves in the same kind of slop that you have and are thriving anyway. Then plant one of those.


  1. Dianne

    I garden by survival of the fittest.

    April 15, 2014 at 8:09 pm
  2. Steve Bender


    We all feel your pain. Our blessings be upon you.

    April 9, 2014 at 10:53 am
  3. Faylyn Jean Hillier

    I am reading this lovely post from the aforementioned snowy Siberia that is Minnesota and crying in my snow-filled yard. Not. Fair. I was conceived in the South, and for some reason, my mother thought it would be nice to raise me in this northern, barren, tundra. Every year, come planting time for the rest of the country, I sit and stare at the snow and consider having her committed for making that choice. This post made me realize that even further.

    April 5, 2014 at 9:14 pm
  4. lkwnc

    Loved this post, just after doing a benefit landscape consultation for folks who were gardening in total subsoil in a new lakeside situation. My first recommendation was adding plenty of mulch (to improve the organic % eventually) — and to definitely amend the soil when planting shrubs and trees (much less perennials). What they were working with was totally pathetic –everything (topsoil-wise) had been scraped away. They’d added pine needles, but …. there were red bare patches of soil, too. Nothing will grow in that without some amendment, that’s for sure.

    April 3, 2014 at 9:23 pm
  5. Jim Borland

    Ah, all things in moderation. I agree, but I never use it for amending soils for trees and shrubs unless I further plan on planting around that tree or shrub. Don’t get me started on mycorrhizae.

    April 3, 2014 at 8:11 pm
  6. Steve Bender

    Jim, I agree with you, but I’d say that adding lots of organic matter to a small hole can be detrimental, because the difference in density and texture between the amended soil and original soil is so great that roots tend not to grow beyond the “bowl.”

    April 3, 2014 at 4:19 pm
  7. Steve Bender

    Thank you, Kelly! One of my favorites!

    April 3, 2014 at 4:17 pm
  8. Jim Borland

    I’ll go with science here and science has proven that adding organic matter to the planting hole for trees and shrubs does no good what-so-ever. On the other hand, it has not proven detrimental either. So, if you are in the business of selling amendments, then do so knowing that you have harmed nothing. It has also been proven that most transplanted trees will grow roots at least 3 feet outward during the first year – way, way beyond the original hole diameter and amended soil. One should also know that not all compost is acidic. That made here in the West is decidedly alkaline. The idea behind digging a much wider hole than the rootball stems from the proven fact that roots grow better, thus faster, through soil that has plenty of air (oxygen) in it (also less dense).

    April 3, 2014 at 3:14 pm
  9. Kelly Thorpe Schubert

    Beer choice is spot on

    April 3, 2014 at 11:03 am

Leave a Comment

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s