How to…mulch

by Rhiannon James

A mulch is a loose covering of material over the surface of the soil.

There are two main types of mulch

1) Biodegradable;

2) Non-biodegradable

Mulches have a whole range of benefits in the garden. They suppress weeds; help to retain moisture in the upper layer of the soil by reducing evaporation; can prevent capping and erosion of the soil by rain or heavy watering and help to regulate soil temperature in both hot and cold weather. Many mulches can also improve the look of beds, borders and containers and harmonise the planting. Mulches are best applied in the autumn or spring when the soil is warm but moist.

Biodegradable mulches add organic matter to the soil and include garden compost, well-rotted manure, leaf mould, spent mushroom compost (don’t use around acid-loving plants or on alkaline soils as it often contains chalk), coir fibre and bark chippings. All of these will gradually decompose and be absorbed into the soil with the help of worms and other soil-dwelling organisms, creating a supply of nutrients and an improvement in the structure of the soil – both very beneficial to plants.

Non-biodegradable mulches such as gravel, stone chippings and slate pieces do not improve the fertility or structure of the soil but they do fulfil the other functions of mulches.

Landscape fabric or geotextile membrane is a good option for new beds and borders – the area covered by sheeting can be made attractive by the addition of a layer of gravel or bark chippings.

Things you’ll need

1. Biodegradable or non-biodegradable mulch

2. A rake or garden fork

3. A sharp knife or scissors if using landscape fabric

Step by step

It’s important that the soil is moist before you add a layer of mulch and it’s preferable that it’s warm so you don’t ‘lock’ cold into the soil.

1. Weed the area very carefully.

2. Apply the mulch and spread using a rake or garden fork, avoiding, as far as possible, walking on the soil and compacting it.


3. Spread the mulch evenly, keeping it away from the stems of plants as this can cause rotting.


4. To control weeds the mulch needs to be at least 5cm thick but 7-8cm is preferable.

Using landscape fabric or geotextile membrane

1. Weed the area carefully and dig in well-rotted manure or garden compost.

2. Cut the fabric to fit the bed or border and lay it over the soil, making holes for any plants that are still in the area being covered.

3. Put in any edging needed to stop the covering material, such as bark chippings, spilling over.

4. To add new plants, cut cross-shaped slits in the material and plant through these, tucking the flaps back around the base of the plant.


5. Cover the fabric with bark chippings or other decorative finish.

A final note: Alpines benefit from a mulch of stone chippings or gravel to a thickness of 3-5cm. This prevents rotting by forming a collar around the ‘neck’ of the plant where water could collect.


Leave a Reply