What Is Mulching, And When To Mulch Gardens In The UK

Mulching is a simple yet powerful technique that can significantly improve the health and appearance of your garden. In this article, we will explore what mulching is, the best time to mulch gardens in the UK, and how to mulch a garden effectively. Discover the benefits of using mulch for your garden, the types available, and expert tips on when to apply mulch to maximise your garden’s potential.

Key Info:

• Best Uses: Ideal for covering bare soil and the tops of containers.
• Optimal Timing: Apply in mid to late spring, autumn, or any time for new plantings.
• Difficulty Level: Easy.

Advice for Buying Mulch

When selecting mulch for your garden, choose the right type for your specific needs. If you aim to improve the soil, opt for organic mulches. Remember, organic mulches need replacing every few years as they decompose. If animal welfare is a concern, be cautious with farmyard manure, as it may come from factory farming.

What does Mulch mean?

Mulch refers to unbound coverings or layers of substances spread over the surface of the soil. The benefits of mulching include:

• Retaining soil moisture
• Reducing the need for watering
• Suppressing weed growth
• Improving soil organic matter
• Providing essential nutrients
• Deterring some pests
• Warming up soil in spring
• Protecting plant roots from temperature extremes
• Encouraging beneficial soil organisms
• Creating a barrier for edible crops from soil contact
• Offering a decorative finish

Types of Mulch

Mulch can be divided into two main groups: biodegradable and non-biodegradable. 

Both types help suppress weeds by blocking sunlight and conserve moisture by reducing soil evaporation. Understanding the different types of mulch for your garden will help you make informed decisions on how to mulch a garden effectively.

Organic Mulches

Organic mulches are derived from dead plant material and offer numerous benefits for your garden. They help improve soil structure, provide nutrients, and retain moisture. 

Here are some common types of organic mulch for gardens:

• Leaf Mould: Low in nutrients but excellent for conditioning soil. Simply collect leaves in autumn, store them in bags, and use them after about 12 months.
• Well-Rotted Horse Manure: Packed with nutrients and retains moisture well. Ideal for hungry plants like roses and squashes. Ensure it has rotted for at least two years to avoid nutrient depletion in the soil.
• Homemade Garden Compost: A versatile mulch that retains moisture, suppresses weeds, and improves soil. Create compost from kitchen scraps and garden waste, turning it every few months. It becomes usable in six to twelve months.
• Composted Woodchips or Bark: Slowly decomposes and enhances soil structure by improving drainage and moisture retention. Its dark colour also contrasts beautifully with green plants.
• Mushroom Compost: Light, easy to use, and ideal for lime-loving vegetables like kale and cabbages. Avoid using it on lime-hating plants such as rhododendrons and camellias due to its high pH.

Inorganic Mulches

Inorganic mulches are materials that do not decompose. They offer long-term solutions for weed suppression but do not add nutrients to the soil. Here are some types of inorganic mulch for gardens:

• Rocks or Gravel: Commonly used in gravel gardens, these mulches help retain moisture and suppress weeds. However, they can heat up in the sun and make the planting area too hot for some plants.
• Plastic Sheeting or Landscape Fabric: Effective at weed suppression but can degrade over time, leaching plastic fragments into the soil. Impermeable sheeting can also prevent rain, air, and nutrients from reaching the soil, which is detrimental to plant health.
• Rubber Mulch: Made from recycled tires, it suppresses weeds and decomposes very slowly. However, the potential toxicity from chemicals in the rubber can be a concern for garden soil.

Biodegradable Mulches

Biodegradable mulches are a fantastic choice for enriching your garden. They break down over time, releasing nutrients and improving soil structure. However, they require periodic replacement as they decompose. Some of the best biodegradable materials include:

• Garden Compost: A versatile mulch that retains moisture, suppresses weeds, and enhances soil health.
• Wood Chippings: Processed conifer bark or wood chips break down slowly and improve soil drainage.
• Leaf Mould: Excellent for soil conditioning; simply collect leaves in autumn and use them after 12 months.
• Well-Rotted Manure: Packed with nutrients, ideal for nutrient-hungry plants. Ensure it has decomposed for at least two years.
• Straw: Great for strawberries, helping to retain moisture and prevent weed growth.
• Spent Hops: Useful but poisonous to dogs, so use with caution.
• Seaweed: Full of nutrients and can improve soil structure.

Non-Biodegradable Mulches

Non-biodegradable mulches do not enhance soil fertility but are excellent for weed suppression and moisture conservation. They can also add a decorative touch to your garden. Options include:

• Slate, Shingle, Pebbles, and Gravel: These materials are decorative and effective at weed suppression.
• Sea Shells and Tumbled Glass: Suitable for container surfaces but avoid plastic materials.
• Dark vs. Light Mulch: Dark-coloured mulches warm the soil, while light-coloured mulches like white gravel reflect sunlight and keep roots cooler.
• Sheet Mulches and Landscape Fabric: Sheet mulches or woven landscape fabric are effective for new beds or borders. Slits can be made in the fabric to allow direct planting. While not particularly attractive, these can be hidden with decorative mulches like gravel or bark. Aim to use porous sheets to let rain and watering reach the root system.

To keep your lawn in the best condition, try these lawn edging ideas.

When to Apply Mulch

Knowing when to mulch your garden in the UK is crucial for maximising its benefits. The best time for mulching gardens in the UK is from mid- to late spring and autumn. In this period, yearly weeds have not started to sprout, and herbaceous vegetation is either in a dormant state or withering away. Mulching can also be done around new plantings any time of the year to suppress weeds and retain soil moisture.

How to Apply Mulch

Understanding how to mulch a garden effectively can sometimes produce the best results. Here are our recommended tips:

• Beds and Borders: Mulch the entire area, being careful not to smother low-growing plants or pile mulch against woody plant stems.
• Thickness: For biodegradable mulches, apply a layer between 5cm (2in) and 7.5cm (3in) thick.
• Damp Ground: Apply mulches on damp ground post weed removal, but avoid doing so when the ground is frozen.
• New Beds: Planting through mulch sheets is effective for new beds.
• Single Trees and Shrubs: Mulch to the radius of the canopy for best results.
• Ground Covering Plants: Mediterranean plants like Thymus species may be best left unmulched to avoid excessive moisture around stems and foliage.

For quirky ideas for your garden, try these boho garden ideas that are bound to bring plenty of colour in the summer.

How to Mulch During Summer

Mulching in summer is optional but beneficial in retaining soil moisture and suppressing weeds. If you decide to mulch, ensure the mulch is not in direct contact with the plants’ stems or trunks. Spread it around the canopy area. Generally, mulching in late spring and early fall is sufficient.

How to Mulch Your Garden During Autumn

Autumn mulching offers unique benefits. As annuals die and perennials go dormant in early fall, a hefty layer of mulch can keep plant roots and soil warm, control weeds, prevent soil erosion, and retain moisture. Always remove weeds before applying mulch. Avoid mulching in late autumn, as this can insulate the ground and disrupt the necessary dormancy period for plants, crucial for surviving the winter.

How to Mulch Your Garden During Winter

While spring is the ideal time to mulch your garden, mulching during winter has its benefits, especially for newly-planted areas. Mulching after the ground has frozen in early winter can prevent the heaving of plants caused by the freeze-thaw cycle. 

Heaving occurs when alternating freezing and thawing conditions lift the soil and plants, potentially damaging them. To protect your plants, apply mulch around them after the soil freezes. As temperatures warm, gradually remove the mulch to avoid shocking the plants. 

When mulching is complete, you can enjoy your garden from the comfort of the wooden garden lounge furniture.

What Not to Mulch

Although mulching can clearly bring many prosperous results for your garden, it’s important to know what not to mulch. Avoid mulching around plants that spread and trail, such as creeping thyme, grasses, and trailing vinca, as this can hinder their growth. 

Additionally, do not mulch over existing weeds, as it can make them more prolific and harder to control. Knowing when to mulch in the UK and understanding these precautions ensures your garden thrives.

Problems

When applied correctly, mulches typically pose no problems. However, mulches in direct contact with the stems of trees or shrubs can cause stem softening, making them susceptible to disease. To maximise the best results, apply a thick enough layer to block sunlight from weeds, insulate the soil, and reduce water evaporation.

• Quality matters: low-quality mulch can introduce weeds, pests, and diseases to your garden. For instance, woodchips might carry the risk of honey fungus. Freshly chipped material can deplete soil nitrogen, so let it decompose for a few weeks before use.
• Maintenance: Mulching may require additional water to reach plant roots initially, but it will eventually help retain soil moisture, reducing overall water needs. Organic mulches are easy to maintain, as they can be replenished with new layers once decomposed. For non-biodegradable options like gravel, ensure a thick application to prevent mixing with soil and surface weed growth.
• Fungus: White fungal mycelium often appears in soil enriched with organic mulch; this is harmless and does not require removal.

How Much Water Could Be Saved?

Using mulch for your garden can significantly aid in water conservation. Organic mulch breaks down and improves water retention in the soil. For instance, you can try this mulch calculator which can estimate how much mulch will be required for each area of your garden – from there, you can follow the steps thereafter for conserving water, especially from mains and rainwater. 

Make May The Best Time To Mulch Gardens In The UK

In summary, mulching is a vital practice to maintain a vibrant, healthy garden. By completing your mulching tasks in May, you can effectively increase soil moisture, reduce weeds, and protect plant roots ready for summer. However, it’s also important to mulch appropriately during different seasons in the UK as well, to a lesser extent compared to May, and maximise the best results for your garden. Don’t forget, you can learn more gardening tips via our blog.

When mulching around trees, make sure to avoid this big mistake.

FAQs

Sources

Calculator Soup. (2022) Mulch Calculator. [online] Available at: https://www.calculatorsoup.com/calculators/construction/mulch-calculator.php [accessed 15/05/24]

Dowle, J., (2023) Why you shouldn’t make this big mistake when mulching around trees. Homes and Gardens. [online] Available at: https://www.homesandgardens.com/gardens/mulching-mistakes [accessed 15/05/24]

Anna Sharples

Anna is the marketing and office manager for Garden Benches – a premium supplier of high-quality wooden benches and other outdoor furniture.