Weed barriers are a practical addition to your garden design to try and cut down weed growth. However, there is some confusion among gardeners whether a weed barrier should go on top of the soil or underneath it.
Weed barrier is traditionally placed on top of the soil, but beneath a layer of compost or mulch placed on top of it. This layer of mulch helps prevent sunlight from penetrating the weed barrier and can act as additional weed prevention.
The type of layers placed over a weed barrier depends on the type of garden plot, bed, or border you’re installing the weed barrier in. Keep reading to learn more about installing weed barriers and the types of mulch that can be used to cover them.
There are advantages and disadvantages associated with putting soil on top of weed barriers.
While soil can be placed on top of weed barriers to encourage the growth of wanted plants vs. weeds, this can also encourage the germination of airborne weed seeds that may become cast over the soil on top of the weed barrier.
In this case, the weed barrier can prevent the growth of weed seeds already in the ground, but will not remove the necessity for pulling weeds entirely.
Putting soil over a weed barrier depends on the following factors:
- The type of weed barrier: Landscaping fabric or plastic weed barriers are usually designed to be placed under rock or rubber mulch, while biodegradable weed barriers like cardboard are designed to decay into the soil.
- The type of garden plot: Cactus and succulent gardens don’t necessarily need soil to grow, while garden plots designed for vegetables and flowers will need access points cut in the weed barrier to allow plant growth in the soil.
Instead of soil, most gardeners put compost and mulch on top of the weed barrier.
This helps protect the weed barrier from airborne weed seeds and prevents them from penetrating the barrier, making any weeds that do germinate more easy to pull.
Here’s a quick video showing how to install weed barrier the right way:
Landscaping fabric is designed to go on top of the soil, but it can also be used as a bottom layer of a border or raised bed before topsoil, compost, and mulch is added.
The downside to placing landscaping fabric underneath soil is that it can tend to hold water after it gets clogged with soil, leading to problems with the garden plot draining properly.
Landscaping fabric is a more practical option for rockscape gardens and other gardens that aren’t focused on growing plants. In these designs, it can be placed under pea gravel or stones to prevent weeds from growing up underneath them.
Installing a weed barrier is a simple process that only requires a few steps.
Here are the steps you should follow to successfully install a weed barrier:
- Remove existing weeds. Removing existing weeds helps prevent the spread of mature weeds that are already present in the garden bed.
- Lay out the landscaping fabric and secure it. Securing the landscaping fabric with garden fabric stakes can help keep the fabric in place and prevent it from bunching up or exposing the soil.
- Cover with compost or mulch. After the landscaping fabric is in place, cover the landscaping fabric with a layer of compost or mulch.
- Cut holes in the landscaping fabric for plants. If you’re intending to use the landscaping fabric in a bed with plants, the fabric will need to be torn or cut to allow the plants to grow through it.
Installing a weed barrier can help take a lot of the backbreaking work out of weeding your garden in the spring and summer. But installing it correctly can make a huge difference in whether the weed barrier acts effectively or not.
The type of mulch you want to use with a weed barrier will depend on what type of weed barrier you’re using. Here are the two primary types of weed barriers and the best mulch to use with them:
- Organic weed barriers: Organic and biodegradable weed barriers like cardboard and newspaper are designed to blend into the soil over time, so organic mulches like pine bark or straw are the best companion mulches for these weed barriers.
- Non-organic weed barriers: Non-organic weed barriers like landscaping fabric and landscaping plastic don’t allow the transmission of oxygen and moisture as easily as organic ones, so they are better suited for rockscape or rubber mulch areas.
No matter which type of mulch you use, adding a weed barrier underneath it can prevent a lot of the weeds you’d have to pull from making it to the surface of the soil.
Weed barriers and mulch can go a long way towards preventing weeds in the garden on their own. However, here are a few additional tips that can help you get the most out of your weed barrier:
- Keep the weed barrier damp but not flooded: Keeping the weed barrier moist will help allow the transmission of water and air through it, preventing the suffocation of any plants that are planted in the bed.
- Try not to damage the landscaping fabric. Landscaping fabric is permeable and easily damaged with a rake or other garden tools. Any breaks in the landscaping fabric are weak spots where sunlight can potentially reach weed seeds underneath.
- Cut the landscaping fabric ahead of time. If you know what plants you’re going to plant in the garden and how far apart they’ll be, cutting the landscaping fabric before you lay it can make it easier to plant the bed later.
Landscaping fabrics can get a bad rap in the garden if they aren’t installed properly. Laying a proper layer of mulch can protect the landscaping fabric from the elements while also holding it in place.
Weed barriers are designed to go over the soil in the garden, but that doesn’t mean they have to be an eyesore.
By applying a proper mulch and compost layer to your garden bed, you can hide your weed barriers while also reaping the benefits of using them.