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Potting Soil Test #1

A Head-to-Head Comparison of Three Potting Soils


Potting Soil Test #1

This photo was taken August 9, 2009, immediately after potting the young, healthy plants. From left to right: Mix A, Mix B, and Mix C.

Photo © Jon VanZile

Date started: August 9, 2009

Plant: Zebra Plant

This is a straight comparison of three potting media. The plants are growing under identical conditions and are all clones from the same grower. The watering schedule varies, based on the moisture retention of each mix (in other words, I'm watering the looser mixes more). No fertilizer was initially added beyond what's listed below.

Mix A

This mix is composed of:

  • 5 parts partially composted pine bark fines
  • 1 part sphagnum peat moss
  • 1-2 parts perlite
  • dolomite lime (level tablespoon per gallon, or 1/2 cup per cubic foot)
  • Controlled release fertilizer
  • Micronutrient powder

This mix is designed to retain its structure over the long haul, through the use of partially composted pine bark fines. It provides superior drainage and aeration to the plant's root zone. The addition of controlled-release fertilizer, dolomite lime, and micronutrient powder supplies nutrients and adjust the mix's pH.

This mix was created by Al Fassezke. Fassezke is a gardening, container gardening and bonsai enthusiast in Bay City, Michigan. He's spent 15 years studying soil composition and working with different formulations, ingredients and amendments, and has developed two basic and readily modifiable fomulas that meet his standards. He's frequently invited to speak to various gardening groups and has contributed articles to a wide variety of publications.

Mix B

This is standard Miracle-Gro Potting Mix. Produced by The Scotts Company, Miracle-Gro Potting Mix is available pretty much everywhere. According to the product label, the mix is based on sphagnum peat moss and includes perlite and a controlled-release fertilizer that will provide three months of nutrients.

Mix C

This is Miracle-Gro Garden Soil for Flowers & Vegetables. Technically, this soil is not designed for container use at all, but as a soil base to be added to outdoor beds. It is made from sphagnum peat moss, composted forest products, aged rice hulls, manure, and a controlled-release fertilizer. The exact formulation might vary from region to region. Because it lacks perlite or some other ingredient to lend structure and air to the media, it has poor drainage and is included here as a control to show how container-specific soils differ from ordinary (or even extraordinary) garden soil.


Three Month Results

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