How To Stop Weeds From Growing in Mulch

When weeds start showing on mulch, it can be very disheartening; not least because it undermines all the planning and hard work that went into mulching the ground. This makes it important to know how to stop weeds from growing in mulch.

Applying mulch on garden beds or landscapes makes a lot of sense for several reasons. Mulch helps the soil retain moisture, adds beauty to the property for those interested in landscaping, and more importantly for gardeners, it is a form of weed control so vegetables can get all the benefits of soil nutrients without competing with weeds.

Stopping weed from going in mulch start right from the type of mulch and the effective use of pre-emergent weed killers before covering the ground with mulch. We would discuss all the measures that help prevent weeds from growing in mulch so you can get the best from the mulch and soil.

How To Stop Weeds From Growing In Mulch

It must be made clear that short of covering your property with concrete and other extreme measures, weeds cannot be totally eradicated. They always come back.

Weeds prevention measures in mulch are ultimately about reducing the severity of the problem and at the initial stage making sure it takes a while before weeds make an appearance. This should give your vegetable time to grow and blossom. In the case of lawn landscaping, these measures ensure you don’t have much work to do when it’s time to eradicate the weeds that inevitably show up.

Any effective weed-prevention strategy in mulch must be done deliberately and should involve some or all of the methods below:

  • Weeding the ground before mulching
  • Use pre-emergent herbicide on the ground
  • Apply the right amount of weed-prevention mulch

Prepping the land via weeding

This’ to get rid of any weed that had sprouted already. Weeding can take many forms including the use of herbicides, by hand, or garden hoe. How widespread the weeds are would determine the method used.

For widespread weed invasion, using herbicides is the recommended technique. A few patches scattered over the land can be removed manually with hands or other farm equipment like a hoe.

If there are no visible weeds though, you can skip this stage and move on to the next.

Using pre-emergent herbicides

These products are used for the control of weeds on farmlands and gardens before the weeds sprout from the ground irrespective of mulching. The herbicides prevent the seeds of the weeds from germinating thus taking care of a large portion of your weed problem immediately and in the medium term.

There are different types of herbicides for eradicating all types of weeds. The good thing is, it doesn’t matter if you have vegetables and other valuable plants. With the right application of herbicides, you can avoid harming important plants and vegetables.

The best time to apply herbicides

It’s always better to apply pre-emergent herbicides before mulching since you are trying to prevent the proliferation of weeds after mulching.

But in terms of season or time of the year, experts recommend that it’s best done at the beginning of spring and fall. To be clear, you could do it at any time of the year, but research shows that spring and fall are the times most weeds sprout.

The most effective weed control strategy using pre-emergent herbicides must acknowledge that different weeds require different strategies due to their different growth cycles and reproductive methods. The seeds of some weeds are known to remain inactive for years in the ground before germinating. These can survive extreme existential issues such as drought, application of herbicides, fire, etc.

Then add that to the fact that even with the best use of herbicides over a long period, wind, rain, humans and other animals can easily bring new weed seeds to your property. That notwithstanding, the aim is about making sure the problem, when it reoccurs, is so small that it can be dealt with easily.

Applying herbicide in Spring

Pre-emergent herbicide application in spring is mainly targeted at annual weeds that sprout in the summer. Broadleaf and grassy weeds belong in this category.

To get the best, the herbicide should be applied when the soil temperature is not less than 55 degrees for at least 3 days a couple of weeks before the regular period of seed germination. You can get accurate soil temperatures readings in your locality from the extension office near you.

The common grassy weeds targeted include:

  • foxtail
  • Goosegrass
  • Sandbur
  • Crabgrass
  • Barnygrass

And the most common broadleaf weeds to control in the spring are

  1. Knotweed
  2. Carpetweed
  3. Clover
  4. Ragweed
  5. Black Medic
  6. Yellow Woodsorrel
  7. Spurge

Applying herbicide in fall

Fall herbicide application aims to prevent the emergent of winter annual weeds. The weeds usually sprout from their seeds during fall and like summer application, timing and soil temperature are important for the best results.

Late summer or early fall is the best time to apply the herbicide depending on your location. Weeds begin to germinate in fall when the soil temperature is below 50 degrees. The appropriate time of the day to apply the herbicide is when the average daytime high temperatures are in the mid 70s. The application should be done for between 3 and 5 consecutive days.

Common winter weeds include:

  • Annual Bluegrass
  • Henbit
  • Common Chickweed
  • Deadnettle
  • Prickly Lettuce

A final word on Pre-emergent herbicides weed control

Always water the land after applying the herbicide so that the active ingredients can penetrate the ground making it easier for the weeds’ seeds to absorb them.

You could always call in the professionals to apply the herbicides if you find it daunting. This could be more effective as they know the right type of herbicides to use for specific weeds.

Applying the right amount of weed-prevention Mulch

One of the main reasons for mulching is to prevent weeds from growing. Unfortunately, this only works to up a point. Without proper measures, it’s not unusual for weeds to grow in the mulch. The tenacity of weeds means they need just a sniff of a chance to thrive.

Preventing weeds from growing in mulch is all about choosing the right mulch and employing the correct mulching methods.

For instance, since weeds need sunshine to thrive, blocking it out the should prevent them from thriving. The best technique is to layer the soil with about 3 inches of mulch to block sunlight effectively.

Mulching to prevent weeds also depends on how long it takes the mulch to decompose especially when you are using organic mulch.

When mulch decomposes, they release nutrients into the soil the weeds can also use to grow. So you want an organic mulch that decomposes slowly. Another advantage here is that it would take a while before you’d need to replace it with a new layer of mulch.

In terms of organic mulches for weed prevention, shredded or chipped bark with coarse texture is the best for mulching. These are slower to decompose than other forms of organic mulch. Besides, because of their texture and weight, they stay put in one place no matter how windy the area is.

Using straw or hay for mulching is also a great idea because they are effective in shading the soil. Unfortunately, weed seeds are found in most of them.

Inorganic mulch

For yards or property with a persistent and widespread weed problem, using inorganic mulch such as black plastic to cover the property is another option. This blocks sunlight from reaching the sun completely but you might have to contend with the rise in soil temperature as a result of the black plastic covering. The roots of some plants might be damaged as a result.

So you’d have to think carefully about using this method.

Landscaping Fabric – Organic mulch combination

The use of landscape fabric alone or in combination with organic material for mulching can also prevent weed from growing. When combined with mulch (landscape fabric is placed under the mulch) they add another effective layer of weed control.

Also known as weed barriers, landscaping fabrics come in two types: woven and non-woven. The woven fabrics are thicker and knitted very tightly while the non-woven fabrics are mostly meshed or spun bound.

Many of them allow nutrients and water from the organic mulch to penetrate the soil. But that takes more time, especially with a slowly decomposing organic mulch.

Tips for using landscape fabric mulch

  1. If you are going to use landscape fabric, the correct way is to start by installing the fabric around your plants, shrubs, and trees.
  2. Ensure one fabric overlaps the next by a few inches at the seams
  3. Use heavy stones or U-shaped pins to secure the fabrics in place.
  4. If you are combining fabric and organic mulch, use your hands to spread the mulch after pouring it on the fabric

Best times to apply organic mulch

The approximate decomposition rate of organic mulch is 1 inch per year. With your 3 inches of mulch, it should take about 3 years for all of it to decompose.

In practice though, the smart move is to re-apply new mulch every year to keep reaping the benefits. And while you are it, that 3 inches of thickness must be maintained consistently.

Towards the end of spring or late fall is the best time to apply mulch especially for folks in the Midwest. At this time, the soil temperature is going up and getting drier: these are perfect conditions for the growth of weeds.

That said, fall isn’t a bad time to apply mulch. Using mulch on the soil at this time is a great way to prep the land for winter.


Mulching a garden, landscape, or flower bed is sometimes necessary to prevent the growth of weeds. But weeds are so tenacious it is common to see them growing even with the best mulch in place. This can be depressing.

This is why many folks go to extreme lengths to find tips on how to stop weeds from growing in mulch. The fact is, there is no permanent solution to weeds, but the best control program ensures the problems caused by them are limited.

Preventing weeds from growing in mulch involves ridding the property of weeds with pre-emergent herbicides before using the most appropriate mulch to cover the land. Landscaping fabric can also be sued in combination with organic mulch to mitigate the weed problem.

When done properly and at the right time, one can stop the growth of weeds for as long as possible allowing vegetables and other plants to thrive unimpeded.

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