Peat Free Compost

What are the peat-free compost alternatives?

Before listing the alternatives, we need to look at the two very different uses and definitions of peat compost.

Compost and peat-free compost to act as a  "Soil Improver"

Most of the UK has heavy clay soil or at best clayey soil. It gets too wet in winter and dries to a hard crust in hot summers. What we really want is a “loamy clay topsoil”.

The best way to achieve this is by adding compost (preferably PAS100 green waste compost) or a mix of compost and biochar to your soil. This will improve your soil as follows:

1. Humic compounds will glue (bind) clay into aggregates – those small lumps that are easy to till/dig

2. Small bits of wood (2-10mm) (or sand (0.5-1 mm) will ‘break up’ clay and allow faster drainage and more aeration

There is absolutely no need to add peat to the soil to "improve" it. It has huge environmental impacts. Please do not buy or add peat (or peat-based composts to the soil. 

Where does Biochar Super Compost (SF60) fit in?

It has more humus and biochar so adds more aggregation, aeration and drainage.  Used in small amounts (10%, 10:1) it is a great addition to improve any clay soil. Realistically, unless you have a robust budget, biochar super compost is going to be added each year, probably supplemented by cheaper PAS100 compost.

We are already starting to see professional growers ask for a range of biochar/compost/soil mixes that take the best of each to create the perfect “topsoil”.  Watch this space!
 

Peat compost and Peat-free "Growing media"

Here things get a bit more “technical”. Many gardeners still attempt to grow plants in compost.  Compost is not a good growing media – it will fail totally or at best give you poor results.

• It is too rich (i.e. has too many nutrients) – certainly for germinating seeds

• It dries out very quickly – although it holds lots of water, it dries (loses it) very quickly.

 (The particles of organic matter dry out really quickly and once fully dry they become hydrophobic which means they are really difficult to re-wet. (Try a simple experiment – take a handful of garden centre compost, a handful of clay soil and a handful of PAS100 compost. Wet each, roll into a ball and leave on a stone to bake in the sun. After 12 hours, tap each ball and watch what happens. The next day, wet each block and try to create a new ball by wetting.)

So compost is not a good growing media on its own. However, peat is a good growing media!  To create a growing media we need to mix ingredients to create a better performance.

Over the years there have been many growing media mixes - probably the best know is the John Innes range. Read our How to make the best plant growing media blog for recipes.

On a commercial scale, horticulture grows all the plants and shrubs we buy in "growing media". In the past, huge tonnage of peat was used. This has been reduced and many excellent peat-free growing media are available.

There are special needs for this commercial growth:

• 100% sterile (free from all pests and pathogens)

• 100% free from weed seeds

• Light in weight, high in volume – to reduce the cost to transport it to garden centres

• It still has to perform well in terms of water holding, drainage and rewetting.

Using PAS100 compost, clay and sand to make growing media does not meet all the above. 

Professional plant growers and those wanting to buy ‘growing media’ will move to use new types of growing media based on wood fibre and/or coir fibre mixed with a range of slow-release nutrient fertilisers and wetting agents.

We hope in earnest that these growing media will call them potting growing media and cease to use the term “all-purpose compost”, and “potting compost”.  (Compost is the product of composting plant material, and growing media will contain very little compost).