One of the best ways to control weeds in your garden is to mulch. Mulch prevents weed seeds from reaching the soil. It also blocks light so existing weed seeds have a harder time pushing through to the surface. This guide explains the best type of mulch to prevent weeds. I’ll also list a few mulches to avoid.
The best type of mulch for weed control depends on where you’re mulching, the climate, your budget, and your personal preference. Wood chips and bark mulch are some of the best options. If you’re on a tight budget, pine needles, grass clippings, and shredded leaves are good options. If you’re looking for an inorganic mulch, gravel can also work well. Black landscape fabric is also an option.
The Best Mulch to Control Weeds
Pretty much all mulches will help keep the weeds down but some work better than others. Some of the best mulches for weed control include:
- Shredded wood mulch- This is one of the best mulches for weed control. The shreds form into a mat that does a good job of keeping the weeds down. It’s also great for the soil. Shredded wood adds nutrients as it breaks down. As an added bonus, shredded wood mulches are attractive. They come in a range of colors and textures. One of the best options is triple shredded wood mulch.
- Wood chips- Wood chips do a good job of blocking weeds. They also add nutrients to the soil as they degrade and they are long-lasting. In addition, they are widely available and they come in a wide range of colors and textures. I like cedar and cypress mulch because they smell nice. They can also help repel certain insects.
- Bark- Bark mulches can do a great job of blocking weeds. They are also long-lasting and attractive. Bark comes in a wide range of textures including bark nuggets and bark dust. Bark mulch doesn’t add as many nutrients as other options. I like pine bark mulch.
- Rock mulch- Rock can also work well to prevent weeds. Pea gravel, lava rocks, and river rocks can all be used. They do a pretty good job of keeping weeds down. They also last forever because they don’t degrade. Rock mulch can also work well for walkways and driveways. One major driveway is that rock can radiate heat, which can heat up your home and garden.
- Shredded leaves- Dry shredded leaves are great for weed control. Best of all, they’re free. You can use the leaves that fall in your yard. Before applying leaves, you have to shred them. If you don’t, they can block air and water from reaching the soil. This can smother your plants. For more info, check out my guide to shredding leaves for mulch.
- Pine straw (pine needles)- Pine needles form into a mat that does a great job of blocking weeds. They are also widely available for free. One drawback is that they don’t add many nutrients as they degrade.
- Rubber mulch- Rubber can do a good job of keeping the weeds down. It doesn’t decompose so it lasts many years. The biggest drawback is that chemicals can leach out of the rubber and end up in your soil. It can also break down and release microplastics. For more info, check out my guide to the pros and cons of rubber mulch.
- Landscape fabric or black plastic sheeting- These materials are specifically designed to block weeds. You install the fabric then put mulch on top of it. It works as a weed barrier. I’ll talk more in-depth about these in the next section.
- Grass clippings- This is another great free mulch option. Collect your lawn clippings in a bag while mowing then use them as mulch to keep the weeds down. As an added bonus, grass clippings will add a lot of nutrients to your garden as they break down. If you use grass clippings, make sure they weren’t treated with any herbicides that could affect your plants.
- Sawdust- Sawdust is another great free mulch option. It can also be used to increase the acidity of your soil if you have acid-loving plants. One drawback is that sawdust can soak moisture out of your soil. It can also deplete nitrogen in your soil as it breaks down. Sawdust works best in a thin layer.
- Straw or hay- Both straw and hay can work well for keeping the weeds down. One problem is that they can contain weed seeds. When you buy straw or hay, make sure they are seed free. These varieties are made for mulching. If you use straw with seed heads, you’ll end up with grass growing in your garden. For more in-depth info, check out my guides to using straw as mulch and using hay as mulch.
- Cardboard- You can use cardboard to smother weeds. Over time, the cardboard degrades away. This can be a great way to deal with an area with really bad weeds. You do have to cover the cardboard with another type of mulch, such as wood chips to prevent it from blowing away. This technique is sometimes called sheet mulching.
- Carpet- One technique some gardeners use is to lay an old carpet over the weeds to smother them. You can then move the carpet on to the next section. This can work well if you’re trying to make a garden in an area with lots of weeds. The problem is that you can only kill weeds on one section at a time. The carpet can also drop fibers over time. The carpet also doesn’t look very nice in your garden.
- Cocoa shells- Cocoa shells are becoming increasingly popular. They come from the tree that is used to produce chocolate. They do a fine job of blocking weeds. They also add nutrients as they degrade. You shouldn’t use these if you have dogs. They contain the same chemical as chocolate. If your dogs were to chew on them, they could get sick.
- Cover crops- Cover crops are living mulch. They are a crop you plant to help reduce weeds by crowding them out. They can also help preserve moisture, add organic matter to the soil, and reduce erosion. In the fall, you can till the cover crop in. Clover is a popular option.
Mulches to Avoid
Pretty much all mulches will help keep the weeds down but there are a couple that you may want to avoid.
Dyed mulch is not recommended. It can do a fine job of weed control. The vibrant colors also look nice. The problem is that it can introduce chemicals into your soil as it degrades. The dyes are designed to be non-toxic but they will remain in your soil for a long time. Dyed mulch is also made from waste wood and recycled wood in most cases. The could have been treated with various chemicals, such as preservatives or pesticides. You don’t want these chemicals in your garden. Particularly if you’re growing vegetables.
Many gardeners also avoid hay mulch because it often contains seeds. Hay is generally used for animal feed so the seeds aren’t removed. If you decide to use hay, make sure it’s seed-free. There are also ways to kill the seeds before you apply it.
Personally, I don’t like to use inorganic mulches like rock or rubber in my flower beds or vegetable garden because they don’t provide any nutrients. I also don’t use landscape fabric or plastic sheeting. I always use organic mulch. The only exception is walkways. Rock can work well.
Pretty much every mulch has some drawback to consider. For example, grass clippings can mold, wood chips could attract termites, lava rock can radiate heat, rubber can leach chemicals, and peat moss is unsustainable. Before choosing a mulch, consider the pros and cons. There is no perfect mulch. Some are better than others.
Should You Use Landscape Fabric Under Mulch to Block Weeds?
Landscape fabric and plastic sheeting are designed to block weeds in gardens. That is really their only purpose. The fabric blocks sunlight from reaching the soil so existing weeds can’t germinate. It is also a physical barrier that prevents existing weeds from growing. It suffocates them. In addition, it blocks weed seeds from reaching the soil. Landscape fabric can do a great job of blocking the weeds.
There are several problems with landscape fabric. First, it only lasts a couple of years. It ends up getting torn. Some strong weeds can grow through it. You’ll also have to cut holes in it when you plant. Over time, it starts to fray and show through your mulch. When this happens, it becomes an eyesore and it needs to be replaced.
Another major problem is that organic matter can collect on top of the fabric and break down. Most commonly, leaves fall on top of the landscape fabric and decompose. Every year, around 0.5-1” of material collects on top of the landscape fabric. After around 2 years, weeds start growing on top of the landscape fabric.
It requires some maintenance to keep landscape fabric weed-free. If you put rock mulch on top of it, you have to keep it clean of debris to prevent weeds from growing. Eventually, weeds will grow on top of it. It’s unavoidable. When this happens, you just have to replace it, which is a big job.
Another issue is that landscape fabric and plastic sheeting can prevent air and water from passing through to the soil. It can also block nutrients from reaching the soil when your mulch decomposes. Landscape fabric is perforated but the holes can get clogged. This can suffocate your plants. Plastic sheeting blocks all air and moisture. This can kill the soil.
Generally, I do not like to use landscape fabric in my garden. It’s really only worth it for permanent beds and walkways. For more in-depth info, check out my guide: Should You Use Landscape Fabric Under Mulch?
How Does Mulch Prevent Weeds?
Mulch prevents weeds in a couple of ways. First, it creates a protective layer for the soil. Mulch blocks weed seeds that blow in or get dropped by birds from reaching the soil surface. The seeds have a hard time germinating in the mulch.
Second, mulch blocks the light so existing weeds have a harder time growing. Weeds have a hard time germinating and growing without any light. Weeds also have a hard time pushing through 3-4 inches of mulch. Even if they manage to germinate, they won’t make it to the surface.
Mulch won’t stop all weeds from growing. There are some tough weeds that can push through the mulch. Perennial weeds will just come back year after year. You will still have to do a bit of weeding, even if you mulch.
Why Control Weeds?
You might be tempted to just leave bare soil on your garden and let weeds grow. After all, they’re just plants, right?
There are some good reasons to get weeds out of your garden. Most importantly, weeds steal resources from your plants. They absorb water and nutrients from the soil. This leaves fewer resources for your plants. As a result, your plants won’t grow as fast or as strong. If you’re growing vegetable plants, your yields will be smaller if your plants have to compete with weeds.
Of course, weeds are also ugly. Your garden won’t look attractive if there are a bunch of weeds growing in it. Weeds are an eyesore.
They also spread quickly. If you have a few weeds in your flower bed one season, they could take over by the next season. They could spread to your neighbor’s yards too, which they won’t be happy about.
If you start spotting some weeds, it’s best to get rid of them quickly so they don’t spread. Removing a few weeds is a pretty easy job. Weeding your whole property is a massive amount of work.
Other Reasons to Mulch
Weed control isn’t the only reason to mulch. Mulch also:
- Retain soil moisture. Mulch slows the rate of evaporation so you don’t have to use as much water or water as frequently.
- Insulate your plants from the heat and cold. The mulch shades the soil to keep it cooler during the summer. It also provides a protective layer between the soil and snow and ice during the winter. This helps keep the soil and your plant roots warmer.
- Reduce soil erosion. It prevents the soil and nutrients from washing away during heavy rain.
- Reduce soil compaction by absorbing some of the impact from rain and foot traffic.
- Adds nutrients to your soil. Organic mulch contains nitrogen potassium, and phosphorus. These are all elements that plants need to grow. As mulch degrades, these nutrients are released into the soil.
- Adds organic materials to the soil, which improves the soil quality and soil health. This helps plant growth.
How to Mulch for Weed Control
- Prepare your garden- Before you begin mulching, take some time to prepare the area. First, you should remove any existing weeds. If you don’t, there is a good chance that they will just grow through the mulch. Weeds are pretty hardy.
- Apply an herbicide (optional)- If you have a serious weed problem, consider applying some herbicide to prevent them from coming back. Make sure you choose an herbicide that won’t affect your plants. For example, you wouldn’t want to use a herbicide that is designed to kill grass if you’re trying to grow corn.
- Choose a mulch- Many different types of mulch can work well for weed control. Shredded wood, pine needles, shredded leaves, grass clippings, and bark are all excellent options. When choosing a mulch, make sure it’s organic. Ideally, it shouldn’t be treated with any herbicides or pesticides and it shouldn’t contain any dyes.
- Lay a weed barrier (optional)- If you choose, you can use landscape fabric to help keep the weeds down. Personally, I don’t like landscape fabric.
- Apply the mulch- For weed control, you should apply a thick layer of mulch. 3-4” is ideal. You shouldn’t apply mulch more than around 4” deep because it can prevent air and water from reaching the soil, which can smother your plants. When applying the mulch, you should leave a gap of around 4-6” around the base of your plants and tree trunks. The mulch shouldn’t touch the stem. This is because mulch can hold moisture, which can cause your plants to rot.
- Water- After you’re done mulching, water thoroughly. Feel the soil below to make sure the water is able to pass through the mulch. If the water isn’t reaching the soil, your mulch may be too thick.
- Re-apply fresh mulch as needed- Organic mulches degrade over time. When the mulch starts getting thin, it’s weed suppression quality will decrease. On average mulch degrades at a rate of about 1-2” per year. Most mulches need to be topped up once every year or every other year. Once your mulch degrades down to about 2” in depth, consider adding a fresh layer. You can apply new mulch over old. You don’t need to remove the old mulch.
When to Mulch for Weed Control
If your goal is weed prevention, early spring is the best time to mulch. The mulch will prevent annual weeds from coming up in the spring. It will also help keep the perennial weeds down.
You can mulch for weed control at any time of year. There is no bad time to mulch. You don’t have to wait. If you choose, you can apply mulch at the end of the growing season.
You Still Have to Do Some Weeding if You Mulch
Mulching won’t eliminate weeds. It will just help reduce them. Some tough weeds will grow through the mulch. It’s unavoidable. You will still have to do some weeding. If you keep on top of it, weeding will be minimal. The mulch will block most weeds.
My Experience
I never used to mulch in my garden beds. Instead, I would just weed regularly. A few seasons ago, I decided to start using some yard waste as mulch. I mulched with grass clippings, shredded leaves, and pine needles. At this point, I have experimented with lots of different mulches.
Free mulches really help keep the weeds down but I didn’t like the way they look in my flower beds. I decided to buy some wood mulch a couple of years ago. It does a great job of keeping the weeds down and it looks beautiful in my flower beds.
Mulching is a great way to keep the weeds down. It makes it much harder for weeds to grow. When you mulch, weed seeds have a harder time reaching the soil. Existing weeds struggle to push through the mulch.
In my experience, pretty much any type of mulch can be used to prevent weed growth. As long as you use a thick enough layer, they all perform about the same. Wood chips, pine needles, and rock mulch all work really well for weed control.
Which type of mulch do you prefer for keeping the weeds down? Share your experience in the comments below!
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