How to Help Your Garden Thrive in a Heatwave: Mulching for Dry Spells

23 August, 2025

While many of us dream of long, hot summers, that kind of garden heat can be brutal for our plants and flowers. Extended periods of high temperatures and little rain can cause plants to wilt, soil to dry out, crops to shrivel, and blooms to fade far earlier than they should. Thankfully, there’s a simple, time-tested technique that can help protect your garden, even during the harshest of summers: mulching.

Using high-quality organic matter like bark, wood chips, or compost is the perfect way to conserve moisture in the soil and provide protection against the unrelenting rays of the sun. Here’s how mulching helps your plants thrive in extreme garden heat and the most oppressive summer conditions.

What is Mulching?

Mulching involves covering the soil’s surface with a protective layer of material. You can mulch with a range of materials: organic mulches such as bark, compost, or straw will break down and enrich the soil, while inorganic ones like gravel or stone shingle remain on the surface. The simple step of mulching brings a host of benefits, especially when you’re gardening in a UK heatwave and the sunshine is relentless.

A natural shield for your soil, mulch locks in moisture, protects plant roots from temperature extremes, and even helps keep weeds at bay. Bark mulch is especially important for water retention and managing excesses of heat and cold within the earth.

Does Mulching Really Help in Hot Weather?

When the mercury rises and rain seems like a distant memory, mulching can actually be a lifesaver for your garden. Here’s how mulch protects your garden in the heat:

Moisture Retention: Mulch slows evaporation, meaning your plants need less frequent watering.
Temperature Regulation within the Soil: Providing a layer of insulation helps keep roots cool during heatwaves (and prevents them from freezing over winter).
Suppression of Weed Growth: Mulch blocks sunlight from reaching the soil, meaning fewer weeds and less competition for precious water.
Improvement in Soil Health: Organic mulches break down over time, enriching the soil.
Prevention of Soil Erosion: The protective barrier that mulch creates helps keep soil structure intact, even in dry, windy weather.

By reducing the stress plants experience in extreme heat, mulching helps them continue to grow, flower, and fruit well into summer.

Heat Stress in Plants: What Happens & How to Help:

What is Too Hot for a Garden?

Every plant has its own heat tolerance, but for many common UK garden plants, temperatures consistently above 30°C can start to cause stress. At this point, soil moisture evaporates rapidly, and leaves may struggle to photosynthesise effectively. Here are some telltale signs that your plants are starting to suffer in the garden heat:

Wilted or drooping leaves, even after watering.
Brown, crispy leaf edges.
Flowers dropping prematurely.
Slow or stalled growth.

Mulching can help by insulating the soil and keeping root zones cooler, giving plants a chance to successfully weather hot spells.

Will Plants Recover from Heat Stress?

In many cases, plants can fully recover once temperatures drop and moisture is restored; however, prolonged stress can cause permanent damage. A proactive approach will give you the best chance of restoring plants to full health. To help them bounce back:

Water thoroughly early in the morning to rehydrate roots.
Provide temporary shade with garden fabric, old sheets, or strategically placed pots.
Avoid heavy pruning during recovery, as this can add stress.
Feed lightly with a balanced fertiliser to support regrowth.

Mulching plays a key role during the recovery period, as it helps maintain more stable moisture levels and temperatures, and protects critical plant structures during this important time.

What Happens to Plants if They Get Too Hot?

When plants overheat, several things happen:

Photosynthesis slows down: high temperatures can inhibit the plant’s ability to produce energy.
Transpiration rate increases: plants lose water faster through their leaves.
They experience root stress: soil dries out, and roots struggle to draw up enough moisture.
They incur cell damage: in extreme cases, plant tissues can be damaged, leading to leaf scorch or death.

Mulch keeps conditions around the roots cooler and more consistent, helping avoid the worst consequences of plants overheating and protecting delicate root structures.

What Are The Best Types of Mulch for Hot, Dry Spells?

Different mulches suit different purposes- for the best mulches for hot weather and heatwave resilience, we’d recommend:

Bark Mulch: Long-lasting, excellent at locking in moisture, and perfect for flower beds and borders.
Compost: Offers both moisture retention and a nutrient boost. Ideal for vegetable patches.
Decorative Wood Chips: Combines the practical benefits of bark mulches with a more polished look and better weed suppression. Does, however, also need replenishing more frequently.
Light Organic Matter: Straw, grass clippings, or leaf mould work well for allotments and veg gardens.

At Bark UK, we stock a range of high-quality bark mulches, compost blends, and wood chips to suit everything from small flower beds to allotments to large landscaped gardens.

How to Mulch in a Garden Heatwave

These few simple steps will protect plants from heat stress and help you get the best results from mulching in heatwaves:

Time it Right: Ideally, you should mulch in spring before the first heatwave hits to give it a chance to settle, but you can apply mulch at any time during summer.
Prep the Area: Remove weeds and water the soil thoroughly before applying mulch.
Use the Correct Depth of Mulch: For optimal protection without smothering the soil, we’d recommend your layers of mulch to be approximately:

Bark mulch: 5-7cm deep.
Compost: 2-3cm deep for delicate plants, 5cm for larger beds.
Wood Chip: 7-9cm deep.

Keep Stems and Trunks Clear: Leave a small gap around plant bases to prevent rot.
Top-Up as Needed: During prolonged dry spells, check mulch levels and add more if it looks like it’s thinning.
For Vegetable Gardens and Young, Delicate Plants, consider lighter mulches like grass cuttings or straw that won’t compact around their fragile structures.

In heatwaves, every little helps when it comes to improving your plants’ chances of survival. Mulching reduces the need for constant watering, keeps soil cooler, and helps your plants cope with the stress of extreme weather. It’s a small investment of time and effort that will reward you all season long, as well as standing your garden in good stead for the colder months, too.

Whether you’re tending a small back garden or managing a large allotment, the right mulch can make all the difference when the summer heat arrives, protecting your plants and keeping your garden looking beautiful, no matter how high the temperature climbs. Find the perfect mulch for your gardens at Bark UK, and hot weather-proof your plants today.