The Soil is warming up; time to mulch!

Bark Mulch

What is mulch?

The RHS defines mulches as:

“loose coverings or sheets of material placed on the surface of cultivated soil.”

You can apply mulch to soil on the ground or on top of composts in containers. There are two types of mulch; biodegradable and non-biodegradable.

Biodegradable mulches

The design purpose of a biodegradable mulch is that they will break down naturally into the soil, releasing nutrients and improving the structure of the soil. The downside of biodegradable mulches is that they will need replacing as the initial application composts down. Some good choices for biodegradable mulches are: garden compost, leaf mold, wood chippings, and seaweed. Used hops can be used but are poisonous if eaten by dogs. Well-rotted manure straw is a great choice around strawberries.

Non-biodegradable mulches

These types of mulches are designed mainly to control weeds and retain moisture in the soil. They are also chosen for their aesthetic value. Non-biodegradable mulches do not release nutrients into the soil or improve soil structure. Items used include: pebbles, stone chippings, shingle, and gravel.

Sheet and fabric mulches

If you are planting up a new large container or border, a sheet mulch or woven fabric might be useful choices. Once you have positioned the materials, you can plant directly through the fabric by making cuts in it. You may want to add a decorative, non-biodegradable mulch on top of the sheets as by themselves they are not attractive. Do make sure that if you choose one of these you choose one that rain can permeate through to the soil.

Why mulch?

For you and your plants!
• Less weeding – mulch suppresses them
• Less watering – mulch retains moisture
• Soil texture is improved
• Wool mulch can deter slugs
• If you are growing fruit and vegetables, mulch provides a physical barrier to prevent them from coming into contact with the soil
• Mulch provides a layer on top of the soil that protects the roots from extreme temperatures and rapid changes in temperature

It can be decorative at the same time as all of the above!

When to apply mulch

The best time to apply a mulch is when the soil is moist and warm, generally late spring and autumn. Apply when you are planting new beds and borders, or add to an existing area when you are working on it. Mulches should be laid over moist soil that is completely clear of weeds and roots. Don’t lay mulch on frozen soil!

How much mulch?

• Biodegradable mulches should be between 2inches (5cm) and 3inches (7.5cm) thick.
• Beds and borders: cover entirely. Make sure you don’t cover low-growing plants or against the stems of plants.
• Planting through mulch sheets can prove effective when creating new beds.
• Specimen shrubs and trees grow well when they are mulched to their canopy’s radius.


• Be careful that you do not spread your mulch so that it is in direct contact with the stems of specimen shrubs and trees.
• Keep an eye out for pests, weeds, and diseases that you might be bringing into your garden.
• Remember that mulch retains moisture in the soil; apply additional water so that it reaches the roots.
• Only replace mulch once it has completely rotted
• Buy from a reputable source to help reduce the risk of contamination

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5 Replies to “The Soil is warming up; time to mulch!”

  1. Top tips, thanks!

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