One of the main reasons for using mulch is to prevent the growth of weeds.
But it won’t stop them completely. Weed seeds are sometimes buried in the soil. And they can be carried into your mulch by animals or the wind and germinate.
The best way to get rid of weeds in mulch beds is by using a pre-emergent herbicide to prevent weed seeds from sprouting. Combined with hand pulling or post-emergent weed killers to take care of the weeds that still manage to grow.
But these aren’t the only methods you can try. Natural alternatives include solarizing the soil, laying down landscape fabric, and even simply cutting them down as they appear.
Let’s take a look at the most effective practices to get rid of weeds in mulch beds and prevent them from returning.
How To Get Rid Of Weeds In Mulch Beds
Pull Them Out By Hand
It can be a lot of work, but sometimes the traditional way is the most effective.
There are two ways you can do this:
You can wait until you see them growing through the top of the mulch and then use your hands to pull the weeds out. But this can result in the weeds breaking off above ground. And if you don’t remove the roots they will often regrow.
A better way is to first rake away the mulch. Then use a hand tool to remove the weed from the ground, including the roots. This takes more work, but the weeds are less likely to grow back.
Weeds can also grow in the mulch when seeds are blown by the wind or dropped by birds.
If your mulch has accumulated dirt and debris it can provide the right conditions for the weeds to grow. But these weeds are very easy to remove by hand without the use of any special tools.
Add A Layer Of Mulch
Mulch prevents weed growth by stopping sunlight reaching the soil, inhibiting germination and the growth of seedlings.
But it doesn’t stop all weeds from growing. Not all seeds need light for germination. And if small amounts of light make it through your mulch it can be enough to support plant growth.
This is more likely the longer the mulch has been in place as some gets blown away or decomposes. So it’s a good idea to replenish it regularly. Wood chips and bark mulch are popular choices to prevent weeds.
To make sure it’s thick enough to stop weeds from growing, try to keep it at least a few inches thick. But you have to be careful not to pile it too thick around the base of trees and in your flower beds as doing so can cause harm to plants.
A thick layer of mulch also makes it harder for weed seeds that land in the area to find their way through to the soil.
Mulching works well to reduce weed growth. But it’s even better when used with a pre-emergent herbicide.
Can I Just Put Mulch Over Weeds?
It’s best to remove weeds before putting down a layer of mulch.
Weeds that are already growing will often continue to grow through the mulched beds.
And you’ll then have to remove the mulch and hoe or pull any existing weeds. This just creates more work for you.
You can use pre-emergent herbicides, such as Preen, to prevent weed seeds from germinating. But they won’t kill weeds that are already growing through your mulch.
First rake your mulch to one side so you can easily apply the herbicide to the soil. Remove any existing weeds by hand. And then apply the herbicide. Follow the instructions on the packet carefully as some pre-emergent herbicides can harm certain types of plants.
If the pre-emergent came as weed killer granules, water them into the soil. Then replace the mulch.
For the best results, you should do this in early spring to control summer annual weeds such as crabgrass, purslane, and knotweed. And again during the fall to control winter annual weeds such as Poa annua, henbit, and chickweed.
But pre-emergent herbicides won’t work to control perennial weeds like nutsedge. For that, you’ll need to use a post-emergent weed killer.
Post emergent weed killers kill the weeds that are already growing through your much.
The best way to use them is to first remove the mulch from the area you want to treat. Then spray the weed killer on the weeds.
Using a post-emergent herbicide makes it easier to get rid of weeds from a large area. And they come in a variety of types. Chemical weed killers are the most common and effective. But not everyone likes using chemicals, particularly around a vegetable garden.
If you choose a chemical product, then make sure it’s a systemic weed killer. These kill plants all the way to the root. Preventing their regrowth.
A good example of a natural weed killer is high-strength vinegar of around 20-30% acetic acid. This will burn and kill the weeds. But because it only kills the parts of the plant it comes into contact with, the weeds sometimes regrow. So you will need to apply it more regularly.
Can You Spray Roundup On Mulch?
Be careful when using non-selective herbicides such as glyphosate. This is commonly found in brands such as RoundUp.
Non-selective herbicides kill all plants they come into contact with. Including any desirable plants you have growing in the area.
To use them successfully, you need to carefully spray the weeds you want to kill using a weed sprayer. Or you can paint herbicide onto the weeds.
Cut Them Down
A quick and easy way to control weeds growing through much is to cut them at the stem, removing the foliage.
This doesn’t kill the roots, so the weeds will still regrow. And you will need to repeat the process regularly. But by removing the leaves you can prevent them from photosynthesising.
This denies them energy. And over time, the weeds will weaken and die. This is a good way to kill weeds naturally. As long as you keep on top of the process of cutting them down.
By cutting the weeds you also prevent them from setting seed, limiting their spread.
Another way of preventing weeds from growing through your mulch is by using landscape fabric.
To make this work, you first need to lay it down so that it covers the soil and then add the mulch on top.
This is an easy way to block weeds while at the same time letting water pass into the soil.
The main drawback is that it isn’t always an effective solution. Weeds that germinate still sometimes find a way to grow through the fabric. And when they do they can be even more difficult to remove.
A cheaper option is to place cardboard under your mulch, or a thick layer of newspaper. This helps to keep the weeds down. And they will decompose over time allowing you to easily plant in your mulch beds in the future.
Solarize The Soil
Solarizing the soil involves heating it up to kill any weed seeds it contains.
It might take you some time, but it can be one of the best methods to eliminate weeds.
Here’s how to do it:
1. First cultivate the soil so that it’s ready for you to plant in the area.
2. Then rake the surface until it’s nice and fine.
3. Water the soil thoroughly.
4. Then cover the area with a piece of tarp, usually made from transparent polyethylene. Don’t use black or white sheeting as they prevent the sun’s rays from reaching the ground.
5. Bury the edges of the tarp in the ground to trap the heat. Use rocks to hold it down at the edges to make sure it doesn’t come loose.
When the sun shines, the heat that’s created in the ground under the sheeting can kill the weed seeds.
Getting rid of them all doesn’t happen quickly. So this method only works when you get plenty of sunlight. Aim to leave the cover in place for a minimum of 4 weeks during the hottest part of the year.
It works best with heavy soils containing loam, clay, or a mixture. These tend to hold more water than lighter soils. And wet soil conducts heat easier than dry soil.
You’ll find it less effective if your have sandy soil in your yard. This drains faster, so there’s less water in the soil to heat up.
Cultivate When Necessary
It’s not unusual for weed seeds to remain buried in the soil for several years waiting for the right conditions to germinate and sprout.
When you cultivate the soil in your backyard you run the risk of bringing these seeds closer to the surface. Giving them access to adequate light and water.
So it’s a good idea to limit how often you cultivate, only doing it when it’s necessary.