What To Put Under Rocks to Prevent Weeds

Landscaping rocks are commonly used as ground cover. Rocks for garden beds have many benefits, including reducing water use and the need to mow. The rocks also do not blow away like lightweight mulch and will not decompose. Rocks are also decorative and can improve the appearance of your garden beds. But, when weeds rear their ugly head, it can put a damper on your parade. Learn what to put under rocks to prevent weeds from infiltrating your garden!

What To Do Before Laying 

Firstly, carefully select the area to lay your landscaping rocks. Ideally, the area should already be weed-free. If it is not, and you need to lay the rock relatively quickly, you will need to dig the weeds out and remove the roots. Alternatively, you can spray the weeds with a non-selective herbicide. Do not spray your bushes as well, since the herbicide will kill them. You could put a large piece of cardboard between the spray area and the bushes, or cover them with plastic. Also, avoid spraying on windy days. Wear protective gloves and a face mask when spraying. 

Household white vinegar will also kill some weeds, although it is not very powerful. A better solution might be to buy horticultural vinegar, which is available online or at a home improvement store.

Pouring boiling water on weeds will kill them, but is not a practical solution for a large area. Make sure you wear appropriate clothing so you do not get burned.

Salt is not advisable as a weed killer because it can kill your existing bushes by changing your soil’s salinity. It can also prevent new shrubs from growing. 

If you do not need to lay the rocks immediately, and the weather is warm and sunny, put plastic over the area and leave it for around six weeks or more. This process will kill the weeds under the plastic. This will not work in cold weather.

A good idea is to put in a steel edging border around 3 to 4 inches high. This will stop weeds, plants, and grasses from laying down roots in the rock beds.

Add plenty of compost to the soil before you lay anything under the landscaping rocks. You will not be able to do this after you have covered the ground and laid your rocks on top. 

Once you are ready to lay your landscaping rocks, you have a few options to put down under them to prevent weeds.

Plastic

A black plastic sheet for garden cover under the landscaping rock is effective at reducing weeds. You can usually get a large sheet, so you can cover whatever ground you need to in one go, without having overlapping pieces, leaving spaces weeds might grow through.

However, it has some disadvantages. Plastic is not environmentally friendly. Sometimes the corners of the plastic will stick up through the rock, which ruins the landscaping. Plastic can also be prone to tearing. The most important downside of plastic is it is not permeable, so rain will not sink into your soil, and moisture cannot be used by nearby plants or your lawn. The lack of oxygen will suffocate any living organisms in the soil. This can lead to root rot  

You could leave holes in the plastic around your bushes to let the air and water in.  

Plastic does not decompose quickly and can be heavy to remove. It can also be cumbersome to dispose of.

If you do choose plastic, select one with UV protection to prevent it from breaking down after a few years. 

Landscape Fabric

Landscaping cloth is a useful weed barrier and will allow water, nutrients, and air to flow to your soil and plants. It is lighter than a plastic cover, and while more expensive than plastic, it lets your plants breathe. 

Landscape fabric generally comes in three types: 

Spun  this is strong and durable and does not puncture or tear. It usually has circular or swirling patterns. You may need to cut holes in it to let plants grow and tree roots to spread. It is strong and can last for many years. 

Perforated – this has pre-cut holes, so air and water can pass through it. It is lightweight. It can tear relatively easily.

Woven – this fabric, with its criss-cross pattern, allows water and air to reach the soil underneath. You may want to cut holes for bigger roots to get through. It does not puncture or tear. 

Landscape fabric prevents your rocks and supporting sand or gravel from sinking into the soil under their own weight. The fabric helps stabilize your soil and reduce erosion. This is particularly important if you live in an area of regular rainfall.  

It is also easy to handle as it comes in a roll. When you lay the weed barrier fabric, overlap the pieces so weeds cannot grow through any gaps. To hold the fabric in place, cover it with rocks; alternatively, you can use landscape staples along the edge. Spread the staples the same distance apart for best results.

You can hide the cloth using a thin layer of mulch, such as stone or bark chips. Take care not to lay too much mulch. Mulch decomposes relatively quickly, which creates enriched soil lying on top of the landscape cloth. Weeds can grow in soil. As the mulch breaks down, it also creates a natural fertilizer for your ornamental plants – but the weed fabric underneath the mulch stops the nutrients from getting to your plants’ roots. 

Landscape fabric does not stop weeds from growing forever. Weed protection usually lasts a few years. Then organic material starts to build up between the rocks, weed seeds are carried in by the wind, and weeds grow again. Sometimes these new weeds can be hard to get rid of because their roots get tangled up in the fabric. 

Even the best landscape fabric will break down after a few years, meaning weeds will grow again. 

Cardboard or Newspaper

Cardboard or newspaper is good at preventing weed growth -in the short term. 

If you choose these to control weeds, put them down as layers of several sheets. This will slow decomposition down. Ensure to overlap each layer to minimize weeds growing up in any gaps. Be careful not to use too much newspaper if you plan to grow plants in the area because this can lead to an excess of carbon in your soil. You may need to use a high-nitrogen fertilizer to compensate. Do not use any colored pages of newspaper to prevent chemical seepage into your soil.

While cost-effective, cardboard or newspaper degrade relatively quickly and lose their ability to stop weeds. Once they degrade completely, the landscaping rocks will start to sink into the soil.

Cardboard or newspaper has to be replaced regularly, which can be time-consuming, but it could be recycled in your garden.  

None of these solutions stop all weeds from growing. You will still need to weed your rock garden regularly to ensure it maintains its appearance.

Final Thoughts