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Is All Peat Moss The Same?

One of the most important ingredients of soilless substrates, peat moss, began in peat bogs shortly after the last ice age about 12,000 – 14,000 years ago. As the glaciers receded, depressions were left in the earth that collected precipitation from rain and snow.

Across Canada, there are different types of peat that formed, depending on the vegetation in the wetland area. However, sphagnum moss is predominant.


How has peat moss formed? 

The acid pH and low nutrient content of the water combined with the cool northern climate was conducive for the growth of sphagnum moss and the accumulation of peat moss. Over time, the environment of low evaporation, acidic pH and low oxygen limited the decomposition of the vegetation.



Different degrees of peat moss

Within the peat bog, there are different degrees of peat moss decomposition depending on the depth. If you were to take a cross section of a peat bog from top to bottom, the surface is composed of recently accumulated peat moss that is blonde in color and fibrous in texture compared to the lower sections of the bog that contain peat that is more humified, dark brown and less fibrous.


Raw sphagnum peat moss: Von Post scale

Raw sphagnum peat moss is graded using the Von Post scale to determine the level of decomposition and humification. The scale ranges from H1 to H10, with H1 being totally un-decomposed plant material and H10 being completely decomposed, based on peat moss color, fiber content and color of water squeezed from a sample.

Van Post Gradation PRO-MIX Greenhouse Growing

"Raw sphagnum peat moss is graded using the Von Post scale"


For example, an H1 grade raw peat moss is completely undecomposed peat which, when squeezed, releases almost clear water. Plant remains are easily identifiable. H4 sphagnum peat moss is slightly decomposed which, when squeezed, releases very muddy dark water. Plant remains are slightly pasty and have lost some of their identifiable features. H10 is completely decomposed peat with no discernible plant structure. 

When squeezed, all the wet peat escapes between the fingers. In North America, most peat moss harvested is in the range of H1-H5, with H1 being blonde and most fibrous and H5 being moderately decomposed peat. Different grades and colors of peat moss are a result of age, decomposition and depth within the peat bog.


Peat blending and grading

Once the peat moss is harvested, different grades are typically blended to achieve specific physical properties. This is because a specific Von Post grade peat moss may not be adequate for the market type. 

For example, H1 peat moss is blond and very fibrous. However, when used alone for growing media, it will shrink in containers over time. H5 is dark brown and is very good for gardening, but it is often blended since alone it can be heavy.


For more information, contact your Premier Tech Horticulture Grower Services Representative:

BLOE          PEEJ              LAWL

Ed Bloodnick
Horticulture Director
US-South East

JoAnn Peery
Horticulture Specialist
US-Central, Canada-Central

Lance Lawnson
Horticulture Specialist
US-West, Canada-West


Troy Buechel
Horticulture Specialist
US-North East

Susan Parent
Horticulture Specialist
Canada-East, US-New England

Jose Chen Lopez
Horticulture Specialist
Mexico, Latin & South America


PRO-MIX® is a registered trademark of PREMIER HORTICULTURE Ltd.

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