How to Mulch Trees in Summer: A Guide for Hot, Dry Weather

Quick Summary: How to Mulch Trees in Summer

Mulching trees during a hot summer can help retain moisture, keep the root zone cooler and reduce competition from weeds.

For most garden trees:

• Water the soil thoroughly before adding mulch
  
• Remove weeds from around the tree
  
• Apply around 5 to 10 cm of organic mulch
  
• Spread the mulch widely across the root zone
  
• Leave approximately 7 to 15 cm clear around the trunk
  
• Never pile mulch against the tree in a mound
  
• Check the mulch periodically throughout summer

Organic materials such as composted bark, woodchip and leaf mould are particularly useful because they conserve moisture while gradually improving the soil.

Correct mulching can make a significant difference during prolonged periods of hot and dry weather, particularly for young and recently planted trees.

Our Full Guide On Mulching Trees In Summer

When temperatures rise and rainfall becomes less reliable, keeping enough moisture in the soil becomes one of the biggest challenges for gardeners.

Watering is important, particularly for newly planted trees, but there is another simple job that can make the water you use go much further - mulching.

A properly applied layer of mulch reduces the amount of moisture lost from the soil, helps protect roots from extreme temperatures and reduces competition from weeds.

During a particularly hot or dry summer, this can make a difference to the conditions around a tree’s roots.

However, more mulch is not necessarily better. Applying mulch too deeply or piling it against the trunk can create a completely different set of problems.

Here’s how to mulch your trees correctly during summer.

Why Is Mulching Important During Hot Weather?

A tree’s roots rely on the surrounding soil for both water and oxygen.

During prolonged hot weather, moisture near the soil surface can disappear quickly through evaporation. Newly planted trees are particularly vulnerable because their roots have not yet spread far enough into the surrounding ground to access larger reserves of moisture.

Mulch creates a protective layer over the soil.

When applied correctly, it can provide several benefits.

It Helps the Soil Retain Moisture

One of the biggest benefits of summer mulching is reduced evaporation.

By shielding the soil from direct sunlight and moving air, mulch slows the rate at which moisture is lost.

This does not mean you can stop watering a newly planted tree, but it can help the soil stay moist for longer between waterings.

It Helps Keep Roots Cooler

Tree roots can be affected by very high soil temperatures, particularly those close to the surface.

Mulch acts as insulation, helping to moderate temperature changes around the root zone.

This is particularly useful during prolonged periods of intense sunshine.

It Reduces Competition from Weeds

Weeds and grass compete with trees for available moisture and nutrients.

This competition matters most around young trees with developing root systems.

Maintaining a clear, mulched area around the tree reduces this competition and means more of the available moisture can reach the tree itself.

It Can Improve Your Soil

Organic mulches gradually break down.

Over time, this adds organic matter to the soil and can improve its structure and ability to retain moisture.

Mulching is not only useful during the current summer. Done regularly, it can help create healthier growing conditions for years to come.

Step 1: Water Before You Mulch

This is particularly important during very dry weather.

If the ground around your tree is already extremely dry, do not simply cover it with mulch.

Water the root zone thoroughly first.

The aim is to get moisture into the soil before adding the protective layer over the top.

A good soak is generally more useful than repeatedly wetting only the top few centimetres of soil.

Once the water has had time to soak into the ground, you can apply the mulch.

Step 2: Remove Weeds and Grass

Before applying new mulch, clear weeds and unwanted vegetation from the area immediately around the tree.

Grass can be a surprisingly strong competitor for moisture, especially around newly planted trees.

You should also inspect any existing mulch.

If old mulch has become heavily compacted or formed a dense layer, loosen it before adding more material. You may not need to add much new mulch if there is already a suitable layer in place.

Step 3: Choose the Right Mulch

Organic mulch is generally an excellent choice around trees.

Suitable materials include:

• Composted bark
  
• Woodchip
• Leaf mould
• Garden compost
• Other well-composted organic materials

Coarser materials such as woodchip are particularly useful around trees because they break down relatively slowly and allow water and air to move through the mulch layer.

Organic materials also have the advantage of gradually contributing to soil health as they decompose.

Step 4: Apply the Right Amount

One of the most important parts of mulching is getting the depth right.

Aim for approximately 5 to 10 cm of mulch.

Finer materials will generally be better towards the lower end of this range, while coarser woodchip can be applied more deeply.

Too little mulch may not provide enough protection against evaporation or weed growth.

Too much can restrict the movement of air and water into the soil.

There is no benefit in creating an extremely deep layer.

Step 5: Keep Mulch Away From the Trunk

This is one of the most important rules of tree mulching.

Mulch should never be piled directly against the trunk.

Leave approximately 7 to 15 cm of clear space around the base of the tree so the trunk and root flare remain exposed.

Why?

Tree bark is not designed to remain constantly buried beneath damp organic material.

Keeping mulch pressed against the trunk can create conditions that encourage:

• Bark decay
  
• Fungal problems
  
• Pest activity
  
• Excess moisture around the base of the tree

Think of the mulch as a wide ring around the tree rather than something that needs to cover every centimetre of soil.

Avoid ‘Volcano Mulching’

You may have seen trees surrounded by mulch piled into a steep mound against the trunk.

This is sometimes called volcano mulching.

Despite being relatively common, it is not a good way to mulch a tree.

The mulch should instead look more like a wide doughnut.

The centre around the trunk remains clear, while mulch extends across the surrounding root zone in a relatively flat layer.

If you remember just one rule when mulching a tree, make it this:

Mulch the roots, not the trunk.

How Wide Should the Mulch Ring Be?

The wider the mulched area, the more of the tree’s root zone you can protect.

For a young tree, aim for a mulch circle approximately 1 to 1.5 metres across where space allows.

Ideally, mulch can extend even further towards the edge of the canopy.

Tree roots spread much further horizontally than many gardeners realise, so there is rarely a need to concentrate mulch in a tiny circle immediately around the trunk.

A wider mulch ring also keeps grass and weeds further away from the developing root system.

Check Your Mulch During Summer

Mulching is not necessarily a one-off job.

During a long, hot summer, check the area periodically.

Organic mulch can:

• Settle
  
• Decompose
  
• Become compacted
  
• Move during watering or heavy rain

If it has compacted, gently loosen the surface with a rake.

If the layer has become very thin, add a little more material to restore the appropriate depth.

There is no need to continuously pile fresh mulch on top. Check what is already there first.

Most importantly, make sure mulch has not moved against the trunk.

Which Trees Benefit Most From Summer Mulching?

Almost any garden tree can benefit from correctly applied organic mulch, but some should receive particular attention during hot weather.

Newly Planted Trees

These should be your first priority. A recently planted tree has a relatively small root system concentrated around its original rootball.

Until those roots establish into the surrounding soil, the tree is much more dependent on moisture close to the planting area.

Trees Planted Within the Last Two Years

A tree may look established above ground while still developing its root system below the surface. Continue monitoring younger trees carefully during prolonged dry spells.

Fruit Trees

Developing fruit places additional demands on a tree. Maintaining more consistent soil moisture can be particularly helpful while fruit is developing.

Trees Growing in Free-Draining Soil

Sandy and other free-draining soils can lose moisture quickly. Organic mulch can help slow this process and gradually improve the soil’s ability to hold moisture.

Common Summer Mulching Mistakes

Mulching is simple, but there are several mistakes worth avoiding.

Applying Mulch to Bone-Dry Soil

Water first during very dry conditions.

Mulch helps retain moisture that is already present. It cannot replace moisture that the soil does not have.

Piling Mulch Against the Trunk

Keep the root flare and base of the trunk clear.

Applying Too Much

More is not always better. An excessively deep mulch layer can interfere with air and water movement through the soil.

Using Too Little

A very thin scattering of mulch will provide limited protection against evaporation and weeds. Aim for a consistent layer of approximately 5 to 10 cm.

Forgetting to Check Existing Mulch

Do not automatically add another layer every year without looking at what is already there. If plenty of mulch remains, simply loosen it and top up where necessary.

Does Mulching Mean You Need to Water Less?

Mulching can reduce the amount of water lost from the soil, but it does not eliminate the need for watering.

This is particularly important for newly planted trees.

Instead, think of mulch as a way of making watering more effective.

Water reaches the root zone, while the mulch helps slow down the rate at which that moisture subsequently evaporates.

During very dry weather, continue checking the soil beneath the mulch rather than judging moisture levels by looking at the surface.

The soil underneath may remain moist even when the mulch itself looks completely dry.

Equally, do not assume that mulch means the soil underneath is automatically wet.

Check before watering.

Mulching During a Drought or Hosepipe Ban

Mulching becomes particularly valuable when water is scarce.

Reducing evaporation means the water already present in the soil remains available to your trees for longer.

If temporary water restrictions are in place, always check the latest rules published by your local water company. Restrictions and exemptions can vary between regions.

Using collected rainwater from a water butt can also reduce reliance on mains water during prolonged dry periods.

Combined with sensible watering, summer mulching is one of the simplest ways to improve your garden’s resilience to drought.

Our Final Thoughts on Mulching in Summer

Mulching is a relatively simple gardening job, but during a hot summer it can have a significant impact on the conditions around your trees.

A good organic mulch helps retain moisture, moderates root-zone temperatures, suppresses competing weeds and gradually improves the soil.

The key is applying it correctly.

Water dry soil first, use an appropriate organic material, aim for around 5 to 10 cm of mulch and spread it widely around the root zone.

Most importantly, always keep mulch away from the trunk.

Get those basics right and your mulch will help make every drop of water go further while providing healthier growing conditions for your trees throughout the summer.

Frequently Asked Questions

Should I mulch trees in summer?

Yes. Summer is an excellent time to mulch trees, particularly during hot and dry weather. Mulch reduces evaporation and helps moderate soil temperatures around the roots.

Should I water before putting mulch around a tree?

If the soil is dry, yes. Water the root zone thoroughly before applying mulch so you are helping to retain moisture rather than covering already dry soil.

How deep should mulch be around a tree?

A layer approximately 5 to 10 cm deep is suitable for most situations. Finer materials generally need a shallower layer, while coarse woodchip can be applied towards the upper end of the range.

Should mulch touch the tree trunk?

No. Leave approximately 7 to 15 cm clear around the trunk. Constant contact with damp mulch can contribute to bark decay, fungal problems and pest activity.

What is the best mulch for trees in summer?

Organic materials such as composted bark, woodchip, leaf mould and well-rotted compost are good choices. They help conserve moisture and gradually improve the soil as they decompose.

How wide should I mulch around a young tree?

Where space allows, aim for a circle around 1 to 1.5 metres across. Extending mulch towards the tree’s drip line can protect an even larger proportion of the root zone.

Can you put too much mulch around a tree?

Yes. Excessively deep mulch can restrict oxygen and water movement through the soil. Avoid repeatedly adding new layers without checking how much existing mulch remains.

Will mulch stop me needing to water my tree?

No. Mulch helps the soil retain water, but newly planted trees in particular will still require watering during dry periods. Check the moisture beneath the mulch to determine when watering is needed.