Mulches And Mulching / RHS Gardening

1. RHS Home
2. Gardening Advice

Mulches and mulching RHS Advice Guide Mulching is generally used to save water, suppress weeds and improve the soil around plants but it also gives your garden a neat, tidy appearance and can reduce the amount of time spent on tasks such as watering and weeding. Mulches help soil retain moisture in summer, rain to penetrate the soil in winter, prevent weeds from growing and protect the roots of plants in winter.

By The RHS Advice Team

• Quick facts
• What is mulch?
• When to apply mulch
• How to apply mulch
• Problems
• How much water could be saved?

The new app packed with trusted gardening know-how

Download app

Quick facts

Suitable for - The surface of bare soil and tops of containers

1

Timing - Mid to late spring, autumn or anytime for new plantings

2

Difficulty - Easy

3

Discover RHS Gardens for free with an RHS Membership

25% off

Join today

What is mulch?

Mulches are loose coverings or sheets of material placed on the surface of soil. Mulches can be applied to bare soil or to cover the surface of compost Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own. in containers.

Depending on the type of mulch Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. used, there are many benefits of mulching Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. including:

• Help soils retain moisture
• Reduce watering
• Suppress weeds
• Improve soil organic matter
• Provide nutrients
• Deter some pests
• Warm up soil in spring
• Protect plant roots from extreme hot and cold temperatures
• Encourage beneficial soil organisms
• Provide a barrier for edible crops coming into contact with soil
• Give a decorative finish

Mulches can be split into two main groups; biodegradable Anything that can be decomposed by fungi, bacteria and micro-organisms, so it doesn’t persist indefinitely in the environment. Biodegradable plastics are usually made from plants, such as bamboo, rather than fossil fuels. Ideally, products that claim to be biodegradable should break down quickly and leave nothing harmful behind. However, they may need specific conditions in order to biodegrade successfully or may produce greenhouse gases such as methane in the process. and non-biodegradable. Both types suppress weeds by blocking sunlight which is needed to germinate and grow weed seeds, and conserve moisture by reducing evaporation from the soil surface.

Biodegradable mulches

These break down gradually to release nutrients To grow well, plants need a wide range of nutrients in various amounts, depending on the individual plant and its stage of growth. The three key nutrients usually taken up from the soil are nitrogen, phosphorus and potassium. Plants also need carbon, oxygen and hydrogen to make carbohydrates — their main energy source. Carbon and oxygen come from the air as carbon dioxide, while hydrogen is drawn from water absorbed by the roots. Other important soil nutrients include magnesium, calcium and sulphur. Most garden soils contain enough of these nutrients to support healthy plant growth. into the soil and help improve its structure. Layers will need replacing when the material has fully rotted down. Among the best materials are garden compost, wood chippings, processed conifer bark, leaf mould, well rotted manure, straw (for strawberries), spent hops (poisonous if eaten by dogs) and seaweed.

Non-biodegradable

Non-biodegradable mulches do not boost the fertility or structure of the soil, but they do suppress weeds, conserve moisture and some have the added advantage of looking decorative. Slate, shingle, pebbles, gravel, stone chippings and other decorative aggregates are often used as a mulch across beds. Sea shells, tumbled glass and similar materials can be used on the surface of containers, but it is best not to use any materials made from plastic. Dark coloured material will warm the soil in the sun whereas light coloured mulch such as white gravel will reflect sunlight and keep roots cooler in strong sunlight.

Sheet mulches or woven landscape fabric can be used for new beds or borders. After laying, slits can be made in the fabric, allowing direct planting through it. The downside is these mulches do not look very attractive, but they can be camouflaged with gravel, bark Bark is the outermost layer of woody plants (trees, shrubs and woody climbers). It is several cells thick and provides protection against physical damage, disease and environmental stresses. Bark comes in a wide variety of colours and patterns, and these can help gardeners when identifying plants. The fissures and crevices of bark on older plants also creates valuable habitat for many garden creatures as well as lichens and small plants. or others materials. To allow rain and irrigation water to reach the roots always choose a permeable sheet as a waterproof layer may cause surface runoff and drainage problems elsewhere.

When to apply mulch

Mulches are best applied from mid- to late spring, when annual weeds have not yet germinated and herbaceous plants are dormant Dormancy refers to a period of inactivity in plants, during which they slow down or stop their growth, conserving energy and resources. This is a natural process that helps them survive harsh conditions, such as winter or drought. Dormancy in seeds is a mechanism that prevents them germinating until environmental conditions are favourable for growth. , and autumn, as plants are dying back. They can be applied around new plantings or to established beds and specimen plants. New plants that need to establish can be mulched at any time of the year when they will benefit from weed suppression and moisture retention in the soil.

How to apply mulch

Beds and borders can be mulched entirely, taking care not to smother low growing plants or to pile mulches up against the stems of woody plants.

• To be effective, biodegradable Anything that can be decomposed by fungi, bacteria and micro-organisms, so it doesn’t persist indefinitely in the environment. Biodegradable plastics are usually made from plants, such as bamboo, rather than fossil fuels. Ideally, products that claim to be biodegradable should break down quickly and leave nothing harmful behind. However, they may need specific conditions in order to biodegrade successfully or may produce greenhouse gases such as methane in the process. mulches need to be between at least 5cm (2in) and ideally 7.5cm (3in) thick
• Lay mulches over moist soil, after removing weeds, when the soil is not frozen
• When creating new beds, planting through mulch Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. sheets is effective
• Single trees and specimen shrubs are best mulched to the radius of the canopy
• As it decomposes over time, a biodegradable mulch will feed your plants and microorganisms in the soil reducing the need for additional soluble feed
• Ground covering mediterranean plants such as Thymus species may be best left unmulched as it can hold too much moisture around the stems and foliage

For more advice on applying mulch see our handy how-to guide.

Choosing and using garden mulches

Problems

If laid correctly there is generally no problem with mulches. However, if they are in direct contact with the stems of trees or specimen shrubs they can cause the stem to soften, making it vulnerable to diseases.

To save water and suppress weeds, the type of organic material you choose is less important than putting on a thick enough layer. Thicker layers will block sunlight from weeds, insulate the soil better and reduce the amount of water evaporating.

Depending on the quality of the material there is a possibility of introducing weeds, pests and diseases to the garden and, with woodchips there is a slight risk of introducing honey fungus.

Once you have added a mulch Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. to the soil you may need to apply extra water to reach the roots of the plants beneath, but mulch will also help rain to soak into the soil, and less water will evaporate, so you should find you need to water less frequently.

Using freshly chipped material such as woody prunings or grass clippings can encourage the microorganisms in the soil to grow but they may use up reserves of nitrogen, leaving less available for plant growth. If you have freshly chipped material, keep it stored for a few weeks before using.

There is no need to remove mulches to apply fertilisers. Fertilisers are spread over mulches in late winter and are washed down to plant roots by rain.

Avoid damaging roots of plants by hoeing Hoes are multi-purpose tools for weeding (especially between rows of veg), loosening the soil surface, making seed drills, earthing up plants, and more. There are various types with different shaped blades. Hoeing to remove weeds is best done on a warm, dry day, so you slice easily through weed stems just below the surface. weeds growing in mulches around permanent plants. Remove weeds by hand and add a further layer of fresh mulch.

Organic mulches can be easier to maintain as they can be replaced by adding another layer when it has completely rotted away. Gravel can sometimes mix with the underlying soil if not applied thickly, encouraging surface weeds.

It is not uncommon for the white fungal mycelium of harmless saprotrophic fungi to be found in soil that has been covered or enriched with an organic mulch. This is nothing to worry about and there is no need to dig out the mulch or white fungal growth.

How much water could be saved?

Organic mulch Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings. breaks down into the soil into materials that help with water retention. The RHS and Cranfield University have developed an on-line tool to help gardeners get an idea of how much water might be saved with techniques such as using mulch and help them make the switch from mains to rains.

RHS Guides, you may also like

• Category: Advice

  How to reuse spent compost

  It’s not uncommon to have some spent compost at the end of each growing season, especially if you grow bulbs or bedding plants in containers. Rather than getting rid of this, which can be difficult and wasteful, there are a handful of ways to reuse it within your garden.
• Category: Advice

  How to deal with garden waste

  Whether you are doing a big garden project or just regular maintenance, it’s likely you will generate some garden waste. Here are some ideas for reusing material within your garden, and some options for removing it.
• Category: Advice

  How to mulch with organic matter

  Covering bare soil with a thick layer of organic matter (biodegradable material) is an easy job that really benefits your soil and your plants, while also suppressing weeds. Here’s how to do it.
• Category: Advice

  Biochar

  Scientists, growers, foresters, greenkeepers and gardeners alike are still learning about the benefits and drawbacks of biochars. The name “biochar” covers a wide range of materials with different properties. Many useful properties of biochar are owed to their physical structure.
• Category: Advice

  Composting

  Recycling your garden waste into home-made compost is both easy and environmentally friendly. Here we look at the basics of making this valuable soil improver and mulch.
• Category: Advice

  Watering

  Watering is key to growing plants well, so here we look at how to get it just right. This not only means providing the water our gardens need, but using it wisely.
• Category: Advice

  Green manures

  Green manures are fast-growing plants sown to cover bare soil. Often used in the vegetable garden, their foliage smothers weeds and their roots prevent soil erosion. When dug into the ground while still green, they return valuable nutrients to the soil and improve soil structure.
• Category: Advice

  Leafmould

  Leafmould is formed from decaying leaves and is an invaluable free soil conditioner. Making leafmould is a great way to recycle what would might otherwise be garden waste into a form of organic matter that’s perfect for mulching. The best leafmould is produced from the leaves of oak, beech or hornbeam.
• Category: Advice

  Mushroom compost

  Mushroom compost can often be bought cheaply in bulk for use as a soil conditioner or mulch. However, it often contains some peat which is no longer recommended for horticultural use due to the damage to peatland ecosystems which contribute to climate change. It is usually available as ‘spent’ mushroom compost, referring to the fact it is the compost left over from mushroom farming.
• Category: Advice

  Organic matter: how to use in the garden

  Organic matter is a much used term referring to a wide range of invaluable materials for feeding plants, improving soil and as mulch. Organic matter is sometimes referred to as 'soil improver' or 'soil conditioner' and soil organic matter as 'humus'. Many gardeners are uncertain of how to use organic matter, so we offer some tips on getting the best from it.
• Category: Advice

  Organic matter: what is it?

  Organic matter is a much used term that can refer to several things, and is easily confused with similarly named activities such as organic gardening. It is no surprise that gardeners are often confused by this very useful piece of horticultural shorthand.
• Category: Advice

  Seaweed products

  Seaweed has been used as a soil improver for centuries, particularly in coastal areas. Seaweed contains several useful plant nutrients, including nitrogen, potassium, phosphate and magnesium. There are dried and liquidised forms available from garden centres and seaweed is a common additive to fertilisers, both organic and non-organic.
• Category: Advice

  Low maintenance gardening

  A low or easy maintenance garden is a necessity or preference for many. Although no garden will be zero maintenance, most gardening activities have a lower input solution or alternative to consider.
• Category: Advice

  Woody waste: shredding and composting

  Most gardens produce waste such as twigs and branches from the pruning of woody plants. This can be troublesome to dispose of in a way that is kind to the environment and to neighbours. Unlike burning, shredding or composting is the ideal solution, resulting in a usable organic material for the garden.
• Category: Advice

  Woody waste: using as a mulch

  Wood and bark from chipped or shredded tree, shrub and hedge prunings makes a useful mulching material in the garden.