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Consumers Beware Potting Mix Choices |
By Carl Wilson, Extension Horticulturist
There's nothing more frustrating then potting a container plant only to experience poor
plant growth. In many cases your lack of a "green thumb" may not be at fault.
A lot of your chance for success is determined by choice of a potting media that allows
you to water effectively.
This is where research-based Cooperative Extension information will help. As the only
Colorado university with horticulture, entomology and plant pathology departments,
Colorado State University is your source for accurate plant growing information.
A two-year research project examined the major potting media sold by garden centers,
nurseries and mass merchandizers. This replicated research indeed showed that potting
mixes produce different plant growth results. Done with geraniums and impatiens, the
following results are likely transferable to growing many other flowering and foliage
plants in containers.
First, chose a true potting media and not something labeled compost. Composts are best
used as organic amendments for outdoor soils. The two composts trialed, Great Plains
Compost and Mushroom Compost, produced poor results.
Second, Hyponex All Purpose Potting Soil and Green Charm resulted in poor plant growth.
Both of these media contain sedge peat, a fine particle material that tests to a low
porosity. There simply isn't enough space within these media for the water and air that
plant roots need to grow successfully. Black Gold All Organic Potting Mix resulted in
significantly less plant growth in one out of two years.
There are definite benefits to growing annual plants in media that may be more costly but
result in better plant growth. Chose a media from any of the following. The study showed
no significant differences in plant growth among these products:
- Home & Garden Showplace Professional Mix
- Fertilome Potting Mix
- Nature's Yield Potting Soil
- Southland Potting & Plant Mix
- Black Gold All Purpose Mix
- Permagreen General Purpose Potting Soil
- Schultz's Instant Potting Soil Plus
- Sunshine All Purpose
Research conducted by Professor James E. Klett, Department of Horticulture and
Landscape Architecture, Colorado State University.
Research funding provided by the Garden Centers of Colorado.
Photograph courtesy of Judy Sedbrook.
