Guide to Mulch

Updated/Fact-Chacked on October 17, 2021 by John

Autumn is a time, along with spring, to add mulch around your plants to provide added protection for the winter months.

This guide will take you through everything you need to know about mulching, making you a mulch expert and your plants will love you for it.

What is Mulch and Mulching?

The term ‘mulch’ is used to describe material that is added to the surface layer of soil to improve water retention, nutrients and provide protection.
Mulch can be organic or non-organic, both have different uses depending on your soil’s requirements.

Mulch V Compost – what’s the difference?  Compost can be used as mulch, being added to the top layer of soil -‘mulch’ simply means a top layer.

Types of Mulch

Organic Mulches

organic mulch made up of homemade compost

Some mulches do not contain many nutrients like leaf mulch  – fallen leaves can be collected at the end of autumn and composted to make mulch, but it can take a good year to break down, unless you have a hot compost kit which can speed up the whole process.

Examples of nutrient-rich organic mulch can be garden compost and well-rotted horse manure or general garden compost bought from a garden centre.

If you are looking at improving water drainage in your beds, then consider a heavy-duty mulch made up of woodchips and bark. These types of mulches are ideal for helping drainage and water retention and don’t heat up the soil, like gravel and slate, when hit by direct sunlight.

Non-organic Mulches

Non-organic mulches include hard natural matter like gravel and stones and man-made materials like plastic sheeting and rubber.
Gravel or stone mulches are generally used to stop weeds coming through, but they also help retain moisture in the soil and have a more decorative quality.

Plastic sheeting or landscape sheeting is sometimes laid over the soil surface to stop weeds, especially if you are creating new raised beds – but these tend to break down over time. We advise not to use any plastics and buy organic-based landscape sheeting. These biological sheets can take up to 3 years to break down if you buy the heavy-duty varieties.

Another great product is Weedguardplus – a paper-based product that stops invasive weeds from growing, but also allows water to pass through. The sheets are opaque which also stops any sunlight from getting through to aid weeds growth.

Benefits of Mulch.

Adding mulch to the top layer of your soil will help the area retain water by reducing evaporation, thus reducing the amount of watering required.  A good mulch layer also stops weeds coming through (but not entirely), so overall mulching will save you time on the labour-intensive gardening jobs.

Certain mulches like horse manure and garden compost will provide additional nutrients for your plants over a period of weeks as it decomposes, ideal for young plants starting out in spring and early summer.

Mulches also provide an insulating layer over the winter months to protect root systems and help retain heat during the spring, bulbs get the temperature required to root.

mulching in autumn to add insulation

You can also use a mulch to add a smart look to your border; coloured mulch can also be added, such as dyed wood barks – as long as they are coloured naturally with vegetable dyes.

What Mulch for What Plant?

Horse manure mulch – best for plants that require a lot of nutrients to grow like roses and edible vegetables.

Composted wood chippings – great for plants that have delicate roots that are not very frost hardy

Mushroom Mulch – Best for plants that like alkaline conditions: vegetables and plants like rhododendrons.

When is the best time for Mulching

Most established plants will benefit from a nutrient-rich mulch being added throughout the year. The best time to add mulch around new plants is springtime,  this will help them develop into strong mature plants and maximise flowering.

Mulching is also good in autumn to help insulate plant roots from the coming winter months.

Mulching Problems

Problems occur when adding mulch if a thin or overly thick layer of mulch is added to your soil.  Too little mulch will not be sufficient enough to aid water retention and will allow the suns rays to help weed growth.  Too much mulch can make it hard for bulb stems to grow through to the surface ideally, you should add around 5 cm of mulch to your soil surface.

tulips growing through a 5cm layer of wood chip mulch

There is a chance of adding pests and disease to your soil from mulching, such as honey fungus, but the positives outway any negatives. You may see common fungi appear, but this is not a problem.

Homemade compost or leaf mulch should be allowed to age and mature; adding to early my use up nitrogen that plants require.

Buying Mulch

If you don’t own a composter, you can buy mulches online or from your local plant supplier.

Mulching FAQ

Is it possible to make your own mulch?

Yes, you just need a composter and slowly add peelings, grass cuttings even paper.

Can I just put mulch over weeds?

Firstly weed out any unwanted plants from the soil, then a good layer of mulch

How can I make mulch fast?

Consider looking into hot composters that speed up the whole process

Should old mulch be removed?

Organic mulch previously applied will completely break down over time and disappear.

Should I mix mulch into soil?

No, you are creating a layer on top of your existing soil

How do you make coloured mulch?

Coloured mulch is created by adding vegetable food dye to wood chips

Is there poop in mulch?

Some mulches may contain horse manure