Homesteading, Gardening, and Off-Grid Living

How Often Should You Replace Mulch and When to Replace Mulch

By: Zac Friedman

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Generally, organic mulch like wood chips or bark mulch lasts 1-3 years, depending on the size and type of wood. Inorganic mulches, like rocks or rubber, can last a decade or more. Some mulches, like straw, hay, grass clippings, and sawdust, need to be topped up every couple of months because they degrade quickly.

In this guide, I’ll outline how often you should replace different types of mulch. I’ll list some signs to look out for that indicate it’s time to add some new mulch. Some mulches last longer than others. I’ll also explain how to maximize the lifespan of your mulch. 

How Often Should you Replace Mulch?

How Long Does Mulch Last?

On average, organic mulches need to be replaced once every 1-2 years. Inorganic mulches can last 4-10 years. In this section, I’ll outline some common types of mulch and their longevity. 

  • Wood chips- Wood chips last around 2-3 years. Every other year, you should add a fresh layer. You don’t need to replace the mulch entirely. You usually only need to add 1-2 inches of fresh mulch. Some types of wood chips last longer than others. Larger wood chips last longer than smaller wood chips. Cedar chips are longer lasting than other types of wood chips. They can last 3-5 years. This is because the cedar wood contains a natural oil that slows decay. 
  • Shredded wood- On average, you’ll need to replace shredded wood every 1-2 years. Shredded wood decays faster than wood chips. This is because the shreds are smaller. They have more surface area for microorganisms to work on. There are different sizes of shredded wood. There is single shredded, double shredded, and triple shredded. The more times the mulch has been shredded, the smaller the pieces. Smaller pieces decompose faster. Triple shredded mulch may need to be topped up once per year. Single shredded may last 2-3 years. 
  • Bark mulch- On average, you’ll have to replace bark mulch every 2-3 years. Exactly how long bark mulch will last depends on the type of tree it comes from and the size of the chips. Large bark nuggets might last 3-4 years. Small bark chips or bark dust might need to be replaced every other year. Smaller varieties degrade faster because they have more surface area. 
  • Straw or hay mulch- Straw and hay degrade quickly. They will need to be replaced every 3-6 months. If you use these mulches, you should expect to apply a fresh layer at least twice per season. Some gardeners apply a little bit once per month. 
  • Grass clippings- Grass clippings last around 3-6 months, depending on the climate where you live. You will have to add a fresh layer 2-3 times per year. They decompose quickly.
  • Shredded leaves- Shredded leaf mulch will last around 6 months to one year. Expect to add a fresh layer 1-2 times per year. Whole leaves will last much longer but they shouldn’t be used as mulch. Large leaves can form into a mat. Matted mulch blocks air and water from reaching the soil. This can suffocate your plants. It’s best to shred leaves before applying them. For more info, check out my guide to shredded leaf mulch. 
  • Rocks (lava rock, pea gravel, river rocks, etc.)- Rock mulch can last basically forever. Rocks don’t degrade. The rocks can get pushed into the soil over time. Small rocks can also wash away. You may need to add a fresh layer every 5-10 years. Installing some landscape fabric under the rocks can make them last longer. 
  • Compost or manure- Compost is already partially decomposed. It’s usually used as a soil amendment rather than a ground cover. If you’re applying compost to your soil as mulch, you should expect to add a fresh layer once per year. 
  • Landscape fabric- On average, landscape fabric lasts 2-4 years before it needs to be replaced. Even though it is inorganic, it degrades pretty quickly. Plants and weeds try to grow through it and tear it. It starts to fray. Eventually, it becomes an eyesore and needs to be replaced. 
  • Rubber mulch- Rubber mulch lasts around 10 years before it needs to be replaced. Over time the rubber can start to fade. Some peaces can get pushed into the soil or washed away. It can also start to break down in some cases. When rubber brakes down, it turns into microplastics. You can extend the lifsepan by installing some landscape fabric underneath. This prevents the rubber sinking into the soil. 

Signs That It’s Time To Replace Mulch

A pile of fresh mulch next to a wheelbarrow

Fading Color or Discoloration

When your mulch changes color, it can be an indication that it’s time to replace it. Most mulches fade or discolor over time. It won’t look as pretty when the color starts to change.

The sun can bleach the mulch and make it dull. This happens to mulch when it has direct sun exposure every day. It’s unavoidable. Mulch that is under trees and shrubs might not fade as fast because it is shaded most of the day.

Most types of wood mulch and bark mulch will fade over time. They won’t keep that deep brown or vibrant red color forever. When they start looking a little dull, you might consider adding a fresh layer. 

Some mulches change color when they start to decay. This happens to pine straw (pine needles). It can lose its nice reddish orange color and turn grey, brown, or black. The same happens to shredded leaves, straw, hay, and grass clippings as they decay. When they start to change color, consider adding a fresh layer. 

Dyed mulches tend to lose their color faster than regular types of mulch. Some of the dye can wash away. Dyed mulch can also be bleached by the sun. On average, they will keep their color for 1-1.5 years. After the color starts to fade, you may need to add a layer. Generally, undyed mulches are preferred because they are better for your soil.

Weeds Start Sprouting

When weeds start growing through your mulch, it can be a sign that you need to replace your mulch or change the way that you mulch. One of the main purposes of mulch is to keep weeds down. It prevents weed seeds that blow in from reaching the soil. It also makes it more difficult for existing weed seeds to germinate and sprout. Weeds have a hard time pushing through the mulch. 

If you start spotting some weeds in your garden, it may mean that your mulch is getting too thin to block the weeds from growing. You may need to add another layer to make your mulch thick enough to stop the weeds.

Pulling weeds in a garden
When weeds start growing in your mulch, it may be time to replace it

You could also consider using landscaping fabric. This can work well under rock mulch but it is generally not recommended for organic mulch. After the mulch starts to degrade, weeds can grow on top of the landscape fabric in the decaying mulch.

It’s also important to note that mulch won’t stop all weeds from growing. Some tough weeds can grow through a thick layer of mulch. You will have to do some weeding, even when your mulch is in good condition. Just because you spot some weeds doesn’t necessarily mean that you need to replace your mulch.

The Mulch Decays Away

Over time, your mulch will decay away. As it degrades, it releases valuable nutrients such as nitrogen, potassium, and phosphorus into the soil. It also adds organic matter to the soil. This allows the soil to hold more moisture and helps it resist compaction. It improves soil fertility. After the mulch decays, you’ll have to add a fresh layer. 

Different types of mulch decay at different rates. Wood chips and bark mulch will decay away at a rate of around 1 inch per year, on average. Shredded wood decays faster than chips. Small chips decay faster than large chips because they have more surface area. Straw mulch, grass clippings, and leaves can decay even faster. They may decay at a rate of 2-3 inches per year. 

When the mulch gets too thin, you’ll have to add a fresh layer. Exactly how long it takes for your mulch to decay to the point where you have to replace it depends on the climate, the type of mulch, and the conditions. For most mulches, this will be every 1-2 years. Most mulches should be around 4” deep. When they decay to 2” deep, you might consider adding a fresh layer on top. 

You Want to Improve Your Home’s Curb Appeal

Fresh mulch around a tree

Replacing your mulch is a great way to increase the curb appeal of your home. If you’re planning to sell your house, that can be the best time to replace your mulch. Fresh mulch can make your home look tidy and well-maintained. The mulch can complement the aesthetics of your home, your landscape design, and your plants. A fresh layer of mulch can really make your house pop. 

If you’re only using mulch for aesthetics, you will need to replace it more frequently than normal. Mulch might perform well for a couple of years but only look good for one year. 

Your Mulch Starts Sinking

Over time, some types of mulch can sink. When you apply it, it may be flush with the edge of your garden. After a year or two, the surface of the mulch may be a couple of inches below where it should be. 

Sometimes, the soil under the mulch can compact and some of the mulch can sink into the soil. This happens with rock mulch. Heavy rainfall can cause the mulch to sink. Foot traffic can also push the rocks into the soil. You can slow this down by using landscape fabric under the rock. You may need to add a fresh layer of rock every 5 years or so. 

Of course, the mulch can also degrade away. When this happens, it will appear that the mulch has sunken. Really, it just turned into soil, which doesn’t have as much volume so the level will appear lower. You can simply add a fresh layer on top to bring the mulch back to the level you want it at. 

You Notice Pests in Your Mulch

If your mulch is infested with ants, termites, earwigs, slugs, snails, cockroaches, millipedes, centipedes, or rodents, it may be time to replace it or switch to a different type of mulch. Some mulch can attract pests and other mulches repel pests.

Generally, pests are most attracted to hardwood mulches. Straw and hay can also attract certain pests. Pests can burrow and nest or even eat your mulch. 

If you have a pest problem, cypress or cedar mulch are great options. These mulches contain natural oils that repel most pests. They don’t like the smell. For more info, check out my guide, How to Repel Pests With Cedar Mulch. Rock mulch is also a good option if you have a pest problem. 

You Notice Disease or Fungus in Your Mulch

a mushroom growing in mulch

If your mulch becomes infected with a fungus or disease, it may need to be replaced. A few fungi to look out for include artillery fungus, powdery mildew, bird’s nest fungi, or root rot. Fungal diseases can be bad for your plants. They can also be difficult to get rid of. 

There are also some bacterial diseases and pathogens that can infect mulch. For example, bacterial blight can be an issue. Replacing your mulch may be the best way to get rid of it. You might also need to get rid of some of your soil. 

You don’t always need to replace your mulch if you spot some fungus. In most cases, you can get rid of fungus by changing the conditions. Watering less, turning your mulch to aerate it, and reducing the depth of your mulch can often help solve the problem.

It’s important to note that mushrooms aren’t necessarily a sign that your mulch is bad. They can be a sign that your garden is healthy. 

A Storm Displaces Your Mulch

A storm can wash your mulch away. Some types of mulch can float away if your garden floods. This is a problem with wood and bark mulches. Flowing water can wash some types of mulch away. Soil erosion can be a problem in some regions. Some mulches can also be blown away by high winds. 

After a particularly bad storm, you may need to replace your mulch. If you experience heavy storms or flooding frequently, it’s a good idea to choose a type of mulch that will stay in place. Your mulch may not last a year if you choose the wrong type.

Some mulches stay in place better than others. Rock mulch can handle storms well because it doesn’t float. Shredded wood, straw, and pine straw can also work well. These mulches tend to entwine and form into a mat. This helps them stay in place.

For more info, check out my guide: How to Keep Mulch in Place and Prevent it from Washing Away.

Your Mulch Starts to Smell Bad

Mulch can start to stink. When this happens, it may be time to replace it or change your mulching technique. 

The most common cause of smelly mulch is anaerobic decomposition. This can happen if your mulch is too thick. The bottom layer doesn’t get enough oxygen. When this happens, microorganisms produce toxins such as acetic acid, ammonia, and hydrogen sulfide that build up in the mulch. These produce a rancid or sour odor like rotten eggs or vinegar. This can harm your plants.

Generally, the cause of this is mulch that is too thick. You can solve this issue by removing some of the mulch. For more info, check out my guide, Why Does My Mulch Smell?

Mulch can also start to smell if it becomes infected with certain fungi or diseases. For example, some types of slime mold can have an unpleasant odor. This is usually caused when your mulch stays too wet for too long or when humidity is high. Watering less or switching to a different type of mulch can help.

Wood chips

How to Replace Mulch

When you replace mulch, you don’t have to remove the old layer of mulch. You don’t have to wait for the old mulch to fully decompose. You can simply add a fresh layer on top of last year’s mulch. 

Ideally, your mulch should be 2-4” deep. When your mulch starts getting down to 1-2”, add another inch or two on top. Be sure not to apply too much mulch. Your mulch should never exceed 4 inches. When your mulch is too deep, it can block air and water from passing through to the soil. This can suffocate your plants. 

Before you add a new layer of mulch, it’s a good idea to inspect your flower beds. If there are lots of weeds, remove them before applying more mulch. Remove any debris like dead leaves or twigs that has fallen on the mulch. Also, make sure your plants are healthy and there are no harmful fungi or diseases in the mulch. It’s also a good idea to rake the old mulch to loosen it before applying an new layer.

After you’re done, you can add a layer of fresh mulch on top of the existing mulch. Try to spread the mulch evenly so it’s not too thick in any part of your garden. 

How to Extend the Life Of Your Mulch

  • Remove weeds- One of the main purposes of mulch is to prevent weed growth. Mulch does a good job of preventing new weeds from growing but it won’t stop existing weeds. Pull any weeds or use an herbicide before applying mulch. This will keep your garden weed-free for longer. 
  • Remove debris from your mulch- If leaves or twigs fall on your mulch, remove it. Debris on your mulch doesn’t look nice. It can also make it easier for fungus to grow.
  • Aerate the mulch- Once in a while, it’s a good idea to rake the mulch to aerate it. Some mulches can form into a mat. This can block air and water from passing through to the soil to your plant roots.
  • Clean your rock mulch- If you’re using rock mulch, be sure to clean any leaves or other debris that falls on it. This is important because the dead organic materials will degrade and fall to the landscape fabric under the rocks. It will build up and weeds will start growing in it. 
  • Consider drainage- If you live in a wet climate, you’ll want to make sure that your garden beds can drain. Make sure the soil is well draining. If you have to, add a soil amendment to improve drainage. Also, make sure the beds themselves can drain. If the mulch gets waterlogged, it fungal growth and disease is more likely. Flowing water could wash your mulch away. Good soil conditions can extend the life of your mulch.

My Experience

I use a couple of different types of mulch in my garden. In my front flower beds, I use shredded wood. I usually add a fresh layer every other year when it starts to get thin or when it starts to look dingy. In my backyard, I use straw, pine straw, shredded leaves, or grass clippings on my vegetable gardens. I use whatever I can get for free. I replace these whenever they start getting thin. Usually 1-2 times per year. I’ll usually add a fresh layer in the spring then another layer in the fall. 

On average, mulch needs to be replaced every 1-2 years. Exactly how often it will need to be replaced depends on the kind of mulch you use and the climate where you live. Some mulches decay faster than others. In hot and humid climates, mulch may decompose faster than in cooler climates. Heavy foot traffic could also cause mulch to break down faster. 

The choice to replace your mulch also comes down to personal preference. If you like your mulch to look vibrant and fresh, you’ll probably want to replace it every year. If you only care about the function of your mulch, you can wait longer before replacing it. 

There are many benefits of mulch. It retains moisture, improves the soil structure, helps with weed suppression, reduces erosion, and adds organic matter to the soil. If you replace your mulch too early, you’ll end up wasting time and money. If you wait too long to replace your mulch, you might start having a problem with weeds. Your plants also won’t benefit from the nutrition that mulch offers. Hopefully, this guide helps you determine when to replace your mulch to keep your garden healthy.

How often do you replace your mulch? Share your experience in the comments below!

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How Often Should you Replace Mulch?

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