Mulching Is A Core Gardening Practice Used Primarily To Conserve Water, Suppress Weed Growth & Enrich The Soil Around Your Plants.
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Beyond these practical benefits, a layer of mulch creates a neat and tidy finish in your garden and can significantly cut down the time you spend on watering and weeding. In summer, mulches help the soil retain vital moisture, while in the colder months, they ensure rain penetrates the ground effectively and offer protection to plant roots. This is my guide on How To Mulch, Mulches and Mulching.
How To Mulch – Quick Facts
Mulching is easy and suitable for the surface of bare soil and the tops of containers. The best times for application are mid- to late spring, autumn, or anytime for new plantings.
What is Mulch?
Mulches are simply loose materials or sheets spread across the surface of the soil or container compost. To be effective, a layer should be at least 2-3 inches thick, but they could be thicker in some circumstances. For example in our food forest we often go 6-8 inches deep as this suppre4sses weed growth far more effectively and soon settles to a 2-3 inch layer which then slowly gets incorporated by worm action.
The benefits are numerous. It helps soil retain moisture and reduces the need for regular watering; it suppresses weeds; it improves soil structure and boosts organic matter (unless a non-biodegradable type – see below); it provides nutrients; it protects plant roots from temperature extremes; and it gives a decorative finish to beds and borders.
Types of Mulch
Mulches are broadly categorised as biodegradable or non-biodegradable. Both types conserve moisture and suppress weeds by eliminating light.
Biodegradable Mulches
These materials decompose over time, releasing nutrients into the soil and improving its structure and fertility. They will occasionally need replacing as they rot down. Examples include well-rotted garden compost, wood chippings, processed conifer bark, leaf mould, well-rotted manure, and spent hops (NB spent hops can be poisonous to dogs. They cause hyperthermia where the dog overheats).
Non-Biodegradable Mulches
These do not break down to feed the soil but are excellent for weed suppression, moisture conservation, and decoration. Examples include slate, shingle, pebbles, gravel, stone chippings, and other decorative aggregates. Darker materials will warm the soil in sunlight, while lighter materials will reflect light and keep roots cooler.
Sheet mulches (woven landscape fabric) are sometimes used on new amenity beds, but yif you decide to use them choose a permeable fabric to allow water to penetrate and prevent runoff. Sheet mulches are often topped with decorative aggregates or bark for a better appearance. Avoid materials made from plastic.
I dislike woven landscape or weed suppression fabrics as they cause so many problems. If you need to lay grit or stone put a good layer of cardboard under it. I do this on amenity beds and it works very well. You get all the benefits but none of the downside.
When and How to Apply Mulch
How To Mulch – Timing
Mulch is best applied in mid- to late spring, before annual weeds emerge and while herbaceous plants are dormant, or in autumn as plants die back. New plants can be mulched at any time of year. Winter is also possible provided you don’t cover frozen soil. ice or snow as it will take a long time to warm up.
How To Mulch – Application
Preparation: Always lay mulch over moist soil that is weed-free and not frozen.
Depth: For biodegradable material, aim for a layer of 2-3 inches deep.
Placement: Cover beds and borders entirely. Do not pile mulch directly against the stems of woody plants (trees/shrubs), as this can cause the stem to soften and become vulnerable to disease—leave a small clear ring around the base. Mulch single trees and specimen shrubs out to the radius of the canopy.
Exceptions: Ground-covering Mediterranean plants, such as Thymus species, are often best left unmulched, as the material can hold excessive moisture around the stems and foliage.
Potential Mulching Issues
If applied correctly, mulches rarely cause problems. However, be aware of the following:
Contamination: Poor quality material can occasionally introduce weeds, pests, or diseases.
Watering: While mulch saves water overall, you may need to apply more water initially to ensure it penetrates the thick layer to reach the roots beneath.
Weeding: Avoid hoeing weeds that sprout in the mulch layer, as this risks damaging plant roots. Remove them by hand and refresh the mulch layer.
Fungal Growth: The presence of the white, thread-like mycelium of harmless saprotrophic fungi in organic mulch is normal and nothing to worry about.
To maximise water saving and weed suppression, the type of organic material is less important than ensuring you apply a sufficiently thick layer.
Water Conservation
Organic mulches break down to form materials that significantly improve the soil’s water retention capacity. This reduction in water loss is key to sustainable gardening.
