What Is Organic Mulch?

Last updated on October 23rd, 2023 at 08:58 pm

You’ve decided to mulch your garden with organic mulch materials, but maybe you’re not quite sure what the differences between your materials are?

Then you’ve come to the right place, because here you’ll learn what organic mulch materials are, what the different materials are and what the respective advantages and disadvantages are.

Organic mulch materials consist of regionally occurring, combustible carbon compounds such as sod, hedge trimmings, bark or other natural fibers. These materials are used primarily for mulching beds, hedges or perennials. In doing so, the soil is fertilized evenly, soil temperature is equalized or increased, and weed growth is suppressed. In addition, organic mulch materials are good at retaining water or moisture and releasing it into the soil.

What are organic mulch materials

In general, one must distinguish organic from mineral mulch materials.

Organic mulch materials consist of regionally occurring, combustible carbon compounds such as wood, leaves or other natural fibers.

In contrast to mineral mulch materials, the carbon compounds contained in organic mulch materials are rapidly decomposed into humus by microorganisms or living organisms present in the soil.

During this decomposition process, the nutrients contained in the organic carbon compounds are released into the soil and the soil is thus fertilized.

Organic materials are mainly used for mulching beds, be it vegetable beds or even perennial or flower beds, grasses or even lawns or hedges.

In doing so, the soil is fertilized long-term and evenly, the soil temperature is balanced or increased, and weed growth is suppressed. In addition, organic mulches are good at retaining water or moisture and releasing it into the soil.

Depending on the mulch material, there are other benefits, such as keeping mold off vegetables or fruits.

Want to know how organic mulches differ from mineral mulches? Then next read through the article I’ve linked here to the right.

However, when mulching with organic materials, care should be taken to treat the soil or beds with a slow-release fertilizer beforehand. Horn shavings are very suitable for this purpose.

This is because the organic mulch materials are slowly decomposed over time by microorganisms in the soil, for which nitrogen is necessary. This nitrogen, which the organisms consume, is ultimately lacking for the plants to grow.

To ensure that there is enough nitrogen for the mulch materials to decompose and for the plants to grow, it is best to fertilize the beds beforehand with about two heaping hands full of horn shavings per square meter.

What are the organic materials for mulching

Can lawn clippings be used for mulching?

Probably one of the most classic mulching materials is lawn clippings. It is free, available in sufficient quantities, easy to spread and can be used almost everywhere.

Before you use grass clippings for mulching, they should be slightly dry. Then you can either spread it on the lawn itself, under raspberries or other fruit trees, on flower beds, or dispose of it in the compost.

However, lawn clippings should only be used as mulch if they do not contain weeds.

Can compost be used for mulching?

Compost can also be used for mulching. Classically, finished compost, or fresh humus, is used in the spring and added to newly established beds and worked into the upper layers.

In addition, you can also work in smaller amounts of compost or fresh humus throughout the year as needed under plants that need a lot of nutrients.

These are, for example, zucchini or pumpkin, which are often planted on the compost itself.

Bark mulch for the garden

Bark mulch is available in coarse or fine versions. In any case, you should make sure that you buy a high-quality, preferably organic product. Otherwise, there may be pollutants or pesticides in the bark mulch.

Since bark mulch is simply crushed, untreated tree bark, it decomposes naturally over time. This creates fresh humus and releases nutrients into the soil below.

To ensure that the nutrients get directly into the soil, you should lightly rake the bark mulch every few weeks. This way it will be newly mixed and well aerated.

Since bark mulch* is made primarily from the bark of coniferous trees, it usually has a slightly acidic pH value.

However, this is usually neutralized during the decomposition process. To be on the safe side, you should fertilize the soil with some horn shavings or lime beforehand.

In addition to the nutrient supply, bark mulch also ensures that the garden does not silt up during heavy rain, that the soil temperature is balanced and that it also prevents weeds.

In addition to the classic brown bark mulch, there is also colored decorative mulch (for example, in red, yellow or gray*) that is often used on paths.

Can straw be used for mulching?

Straw is another very popular mulching material, especially since it is very cheap and easy to handle.

Straw mainly ensures that the soil remains dry, thus preventing mold on plants and fruits. It also promotes aeration and fixes the nitrogen needed for plant growth in the soil.

Straw is mostly used under strawberries, zucchini or squash. The straw ensures that the fruit does not get dirty and is protected from moisture and mold.

However, since straw contains more carbon than nitrogen (i.e., have a wide C:N ratio), the creatures and microorganisms in the soil need additional nitrogen to decompose the straw in the first place. Fertilizing the soil before mulching with a nitrogen slow-release fertilizer such as horn shavings is suitable for this purpose.

Mulch paper / mulch film / weed fleece

Mulch paper* or mulch foil* or mulch or weed fleece has mainly the advantage that it increases the temperature of the soil and retains moisture better.

You can use it especially with various vegetables, such as tomatoes, cucumbers or even lettuce.

Less advantageous or not recommended to use with larger shrubs, ferns or grasses.

Can leaves or hedge trimmings be used for mulching?

Leaves or hedge cuttings are also suitable for mulching, especially under larger plants or in places that are not visible at first glance.

By this I mean for example under shrubs, perennials, grasses or even under raspberry bushes or fruit trees.

However, you should pay attention to two things when mulching with leaves or hedge trimmings:

Foliage, especially oak foliage (but also from chestnut and walnut), can sometimes have an acidic effect or be infested with pests. This means that during the decomposition process, tannic acid is usually released, which causes the pH value of the soil to drop and become acidic. Therefore you should give oak leaves only under plants that tolerate an acidic soil. Here you can find out which ones these are
Hedge clippings should be of a suitable size for mulching. More specifically, you should not use coarse branches or woody debris for mulching. Hedge clippings should be as small or fine as possible so that they spread nicely and decompose as easily as possible.
Similar to straw, leaves or hedge clippings normally have a wide C:N ratio, meaning a very high percentage of carbon and a low percentage of nitrogen. So to ensure good decomposition without the soil suffering a nitrogen deficiency, you should enrich it with nitrogen.

You can do this either classically with horn shavings or by mixing in lawn clippings, which are quite nitrogenous.

Can I use the stalks of green manure or perennial waste for mulching?

Furthermore, you can also use the stems of green manures or perennial waste for mulching.

Both hardy and freezing green manure can be used for mulching in spring or fall. To do this, simply spread the mown stalks on the beds or shred them a bit more in the spring and work them in.

Can wood chips be used for mulching?

Wood chippings are also recommended as mulching material. Wood chippings, as the name suggests, are simply wood chopped into small pieces, which you can order here for example*.

A big advantage of wood chips as mulch material is that they keep slugs away because they can hardly or not at all climb over the scratchy wood chips.

Thus, wood chips are ideal to use as mulch material on paths or even under shrubs, grasses, raspberry plants or fruit trees.

Otherwise, you can also use wood chips in the vegetable patch as a protection against slugs. You can find out how to do this here.

Like leaves and straw, wood chips also have a wide nitrogen-carbon ratio (wide N-C ratio). This means you should mix in nitrogenous materials when mulching, such as lawn clippings or horn shavings.

This will ensure that the plants will not suffer from nitrogen deficiency.

Can cabbage or rhubarb leaves or potato foliage be used for mulching?

Similar to the stems of perennials or green manure, cabbage or rhubarb leaves or potato foliage (i.e. the green leaves of the potato plant) can also be used for mulching.

These can be left on the bed directly after harvesting in the fall, where the leaves will slowly decompose.

You can leave the leaves on the beds throughout the winter without any problems, which will further protect them from cold, evaporation and weed growth.

Remember that you should not dig up a bed with normal soil in the fall, but only in the spring. If you want to know why not, and what are better alternatives to digging up then check here.

Can you use nettles and comfrey leaves for mulching?

Nettles or comfrey leaves are probably one of the best mulching materials you can find in your own garden.

They grow quickly, but also decompose very quickly on the beds. In addition, they can be used for mulching but also make nutritious slurry or fertilizer.

Because of the many nutrients contained in nettles and comfrey, they are very good for mulching heavy growers such as tomatoes, potatoes, cucumbers, squash, cabbage or peppers.

Dried or slightly wilted nettle or comfrey leaves are best. Because then it goes even faster until they rot on the beds and give the valuable nutrients to the plants.

Can cocoa shells be used for mulching?

Cocoa shells (like these*) are great for mulching the garden because of several advantages over other organic mulch materials:

Cocoa shells are also officially considered a natural, organic fertilizer, which is not the case with bark mulch, for example. Cocoa shells, like conventional fertilizers, contain nitrogen, phosphate, potassium oxide and magnesium oxide in something like a 3.5-1.5-4.5-1 ratio.
Due to the nature and material, cocoa shells can contribute very positively to water regulation
Moreover, cocoa shells actively suppress even very fine weeds
Cocoa shells do not acidify the soil as bark mulch or pine bark does over time.

However, cocoa shells are only suitable for mulching beds and less suitable for mulching paths. On the one hand, because on paths the fertilizing effect would be given away and, on the other hand, cocoa shells can become very slippery in rain or moisture.