Organic mulches are an essential component of sustainable gardening practice. Using them is important for a number of reasons.
It is vital, however, to use the right mulches, and to use them correctly. Because when the wrong mulch is used or mulches are used incorrectly, they can do more harm than good.
Unfortunately, mulching is one of the organic gardening practices most commonly misunderstood. So we’ve put together this organic mulch guide to help beginners understand what can be a confusing topic when not properly understood.
Table of Contents
What is Organic Mulch?
Organic mulches are natural materials derived from plant or animal matter that are spread over the soil surface around your plants.
In a ‘no dig’ system, rather than digging compost or other fertilisers or soil amendments into the soil, these are laid as mulches on the soil surface.
The harvest that can be obtained from a ‘no dig’ system has been shown in studies to be larger and healthier than one produced using a more traditional ‘dig’ method of gardening.
Learn more about mulches and feeds for your polytunnel and keep the soil ecosystem flourishing by embracing the ‘no dig’ polytunnel gardening techniques and you could be eating better than ever before, as well as learning from this organic mulch guide.
Benefits of Mulching
Mulches are extremely important for those who try to garden in as eco-friendly and sustainable a way as possible, both in a polytunnel and in other types of garden.
Mulching is the main method by which ‘no dig’ gardeners add nutrients to and protect the soil. Rather than digging in organic matter, gardeners adhering to this way of doing things will lay organic matter as a mulch over growing areas and around plants.
There are a number of benefits to the ‘no dig’ system, which arise from the flourishing soil ecosystem.
Firstly, since the soil is left (mostly) undisturbed, the organisms that live within it are better able to do their work. Earth worms will help to aerate the soil as they move through it, also enriching the soil as they go. Fungal and bacterial networks can transport nutrients and work their magic without disruption.
There is a lot going on in the soil, and we rely on it working as a fully functioning ecosystem in order to grow healthy crops. It makes sense to allow it to remain as undisturbed as possible in order to do its job.
By choosing the right mulches for the right places from this organic mulch guide, organic gardeners can help to maintain good soil, and provide for the plants that are grown there.
They are used to:
- Add nutrients and build soil fertility.
- Improve the structure and capacity of the soil.
- Protect bare soil from nutrient loss and erosion.
- Retain more moisture in the soil and help reduce water use.
- Suppress weeds and reduce weed growth.
- Protect plants over winter by providing some insulation for their roots.
Mulches can be specifically chosen to provide one or more of these services. Most mulches will not serve one, but rather multiple functions.
Mulch can also help us increase the biodiversity in our gardens – providing habitat for ground-dwelling wildlife and also helping to improve biodiversity of micro-organisms like bacteria and fungi in the soil ecosystem.
Disadvantages of Organic Mulch
The right mulch can always be extremely beneficial. But the wrong mulch, or a mulch laid in the wrong place or in the wrong way can bring a range of problems and disadvantages. This is why it is so important to choose the right ones.
If organic mulch is piled around the base of stems or tree trunks, it can cause them to rot.
If some organic mulch is laid to thickly, it can potentially mat and compact creating a barrier that water cannot easily pass through to reach plant roots.
Some mulches laid too thickly may also begin to smell, if the mix becomes anaerobic.
Some woody mulches lead to nitrogen sequestration, temporarily reducing nitrogen availability as they decompose, potentially leading to nitrogen deficiency for some plants.
On the other hand, some mulches too high in nitrogen can ‘burn’ some plants.
Mulches can attract not only beneficial wildlife but also some pest species, and occasionally, issues with pests such as slugs, snails or rodents may arise.
These are just some of the issues that can arise when the wrong mulches are used or when mulches are used incorrectly.
Types of Organic Mulch
When deciding which organic mulch to use in a specific location and for a specific purpose, it can be helpful to think about four main categories of mulch that you might use:
- Partially-decomposed organic matter.
- ‘Green’ (nitrogen rich) materials.
- ‘Brown’ (carbon rich) materials.
- Plants which serve as ground-cover and act as a living mulch.
If it important for beginners to understand that mulch is not something that you have to buy. It is often something that is derived from your garden, obtained for free. From there, you can begin integrating it into your domestic polytunnel.
Partially-decomposed organic mulch
In this category are mulches such as:
- leaf mould.
- well-rotted manure.
‘Green’ (nitrogen rich) mulch
In this category are:
- grass clippings.
- other green, leafy material (like material from pruning, or chopped and dropped plants).
‘Brown’ (carbon rich) mulch
In this category are mulches made from:
- wood chip, bark or other woody material.
- dried autumn leaves and other dead/ dried plant matter.
- straw or bracken.
Living mulches are living groundcover plants used to cover the soil. These are carefully selected to bring benefits to the plants that they surround without increasing competition too greatly.
A living mulch is a specific type of companion planting. The plants are specifically chosen to cover and protect the soil. But they can also aid the crops that they are grown between in other ways.
For example, they can attract bees and other pollinators. Or other beneficial insects which help to keep sap-sucking pests population numbers down. Such as ladybirds and hover flies, for example. They might also help in drawing other beneficial wildlife to the garden.
Some living mulches might also help keep away, confuse or distract unwanted pest species. So might help in keeping your main crops safe.
Where are Organic Mulches Used?
Organic mulches can be used around the plants in almost any growing area. They are also used to create new ‘no dig’ garden areas in the first place, and to prepare the soil for a new perennial planting scheme such as a new forest garden.
Plants in all four categories above are commonly used in an annual vegetable garden. But mulch materials too high in nitrogen can potentially ‘burn’ tender young plants. And woody materials can ‘rob’ the soil of nitrogen temporarily and therefore create short-term nitrogen deficiencies.
So if wood chip or other woody material is used in annual cultivation, it should be used in conjunction with other materials that can add nitrogen back into the system.
Specific mulches are used in specific ways to provide certain nutrients or to provide certain other specific benefits to the plants that they surround.
This article should provide further assistance in choosing the right mulch for the right situation.
How to Use Organic Mulches
To create new growing areas, organic mulches are typically laid over the ground in layers.
Often, to build soil and make new beds or borders, layers of brown and green materials will be topped with homemade compost or other similar material. Raised beds created in this way include ‘lasagna’ beds and hugelkultur mounds.
Sheet mulching areas is also a strategy employed to speed ecological succession in the creation of forest gardens or other perennial planting schemes.
This often involves adding a relatively thick layer of mostly woody materials that encourage fungal soil ecology to develop and the formation of a healthy woodland or forest rhizosphere to take place before the functioning ecological system can take over and continue to improve and nurture the soil on its own.
Mulches are typically laid and replenished in the spring, and sometimes in the autumn too. They will often remain in place over the summer and are especially beneficial for soil health, plant health and water conservation during the warmest part of the year.
Plants will benefit from mulching in spring since weeds will not have taken root yet, and the soil will be warming up, and it is necessary for winter when the plants have begun to die back to protect their roots for next year.
However, you can mulch new plants that need to be established at any time of the year since weed suppression and extra moisture will boost their growth.
Choose your mulches carefully and apply them correctly and at the right times and you will surely soon reap the rewards in your garden, thanks to reading this organic mulch guide.
Can I work inside my polytunnel during heavy rainfall?
Absolutely! One of the primary benefits of a polytunnel is that it allows you to continue gardening activities even during inclement weather, including heavy rainfall. The polytunnel provides shelter, ensuring you and your plants stay dry.
How does rain affect the temperature inside the polytunnel?
Rain can cool the environment inside the polytunnel, especially during heavy downpours. The drop in temperature can be beneficial during warmer months, but it’s essential to monitor the conditions to ensure it doesn’t become too cold for heat-sensitive plants.
Do I need to worry about flooding inside my polytunnel during rain?
Properly installed polytunnels should have adequate drainage to prevent flooding. However, during prolonged heavy rainfall, it’s a good idea to check for any water accumulation and ensure that the ground inside the polytunnel is draining effectively.
How can I improve the drainage inside my polytunnel?
To enhance drainage, consider raising the beds inside the polytunnel, adding organic matter to the soil to improve its structure, or even installing a gravel or sand base layer. Properly positioned trenches or channels can also help direct excess water away from the polytunnel.
BBC Gardeners’ World Magazine. (2020) No-Dig Gardening Guide. Gardener’s World. [online] Available at: https://www.gardenersworld.com/how-to/grow-plants/no-dig-gardening-guide/ [accessed 25/08/23]
Hayes, B., (n.d.) Sheet Mulching: A Quick Guide to Getting Started. Morning Chores. [online] Available at: https://morningchores.com/sheet-mulching/ [accessed 25/08/23]
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.
To get in touch, visit https://ewspconsultancy.com.