What is peat? formation & use in the garden

Kati
Kati
Kati
Kati

I am a qualified gardener and horticulturalist and love everything that grows! Whether it's a shrub, a tree, a useful plant or a supposed weed: for me, every plant is a little miracle.
In the garden I look after my 13 chickens, grow fruit & vegetables and otherwise observe how nature manages and shapes itself.

Favourite fruit: Blueberry, apple
Favourite vegetables: Braised cucumber, kale, green pepper

Time and again you read about peat-reduced soils etc. But what is peat exactly and how is it formed? We reveal whether you need peat in the garden and why it is better to use it sparingly.

A stack of peat drying
In the sod peat process, the peat is cut into so-called sods and dried [Photo: John And Penny/ Shutterstock.com]

Peat is still a basic material in many potting soils. We explain what peat is actually all about, how it is formed and, at the same time, take a look into the near future. After all, peat will soon only be used in small proportions in horticulture to protect the climate and valuable ecosystems.

What is peat?

Peat is a form of humus that forms in bogs from dead bog plants due to the lack of oxygen underwater and an acidic pH. Peat consists of partially decomposed and preserved plant remains, primarily peat mosses (Sphagnum).

Since there are different types of bogs, peat can also vary in its properties. Peat from fens is strongly acidic to slightly alkaline (pH 3.2 to 7.5), highly decomposed and rich in nutrients. Raised bog peat, on the other hand, is strongly acidic (pH 2.5 to 3.5), with a comparatively weaker decomposition and is low in nutrients.

Only the peat from raised bogs is used for horticultural purposes. Old black peat is hidden several metres below the ground. It is fine and its plant parts are barely recognisable. Younger white peat is found in the upper layers of the raised bog. Here, you can still clearly see the structure of the barely rotted plants.
Due to its beneficial properties, raised bog peat is ideal for compost. Unfortunately, however, its extraction and use damage the environment both regionally and globally – for this reason peat endangers the climate and species in the garden.

A person holding a peat stack
Plant fibres can still be seen in weakly to moderately decomposed peat [Photo: IRINA ORLOVA/ Shutterstock.com]

Tip: Some readers may still remember that before it was used in potting soils, peat was burned for heating or used as bedding in animal barns.

How is peat formed?

Peat is formed by the accumulation of non or barely decomposed organic material under oxygen exclusion in water-saturated bogs.

The beginning of peat formation in bogs dates back around 12,000 years. Since peatlands store a lot of rainwater or are also fed from groundwater, they are saturated with water. Most decomposing organisms cannot live and do their work under these conditions, or can do so only poorly. For this reason, an increasingly thick layer of plant material accumulates in bogs over time. This is reinforced by the establishment of very high acidity in some types of peatlands. Since this deposited plant material consists largely of carbon compounds, peatlands are rightly considered giant and important CO2 reservoirs that remove carbon dioxide from the atmosphere. However, when peat is used it is released again – fueling the greenhouse effect.

Peat in moorland
Over the millennia, the peat layers in the moor become thicker and thicker [Photo: Stephen Barnes/ Shutterstock.com]

Peat in the garden: use and alternatives

Peat has been used in horticulture for several decades. Since it has physical and chemical properties that are very conducive to plant growth, for a long time it was impossible to imagine compost without it.

Thus, due to its favourable pore size distribution, it can store a lot of water without causing the roots of plants to suffer from oxygen deficiency. In addition, its pH value is very low and it can be easily adapted to the needs of each plant with the help of lime. When dry, it is quite light, which simplifies transportation. And last but not least, it is very low in nutrients. The nutrient content can therefore also be individually adjusted for the plants to be cultivated. It is also popular in peat beds because of its high acidity: rhododendrons (Rhododendron), hortensias (Hydrangea), skimmias (Skimmia japonica), lavender heath (Pieris japonica) and blueberries (Vaccinium) benefit very much from planting with peat.

However, peat is becoming scarce: according to current forecasts, global peat reserves could only cover our needs for a few more decades. In addition, the extraction of peat – no matter how gently it is carried out – releases large quantities of carbon dioxide into the atmosphere. Complete abandonment, or at least a sharp reduction in use, is therefore a worthwhile goal in terms of climate change. Professional horticulture and, of course, environmental associations as well as nature conservationists have also recognised this: peat-free and peat-reduced compost is the future and compost containing peat should be a thing of the past as soon as possible.

Peat-free or peat-reduced compost can be mixed from very different components: wood fibre, compost, sand, clay minerals, various coconut materials, perlite and xylitol mixed in the right proportions can satisfy the needs of our plants just as well as peat. Coconut pulp (also called cocopeat, alsococonut peat), for example, has a very similar water and air capacity to peat. Clay minerals and compost provide good nutrient-holding capacity and perlite provides good structural stability.

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