A post-emergent herbicide kills weeds as soon as they sprout. Choose a non-selective herbicide such as one containing glysophate so it will kill nearly any kind of weed that appears. Care is essential when spraying the non-selective herbicide near your bushes because it can harm or kill bushes as well as weeds. Protect the bushes from herbicide drift by placing plastic or a large piece of cardboard between the bushes and where you spray, and spray only on days that aren’t windy.
Adding underlayments between the rocks and the soil creates a weed barrier that helps prevent weed seeds from touching the soil. If you already have rocks in place, rake them away temporarily while you install the underlayments. Choose landscape fabric or black plastic as the underlayments.
Plastic is the best weed barrier under rock, but water won’t pass through it to feed the bushes’ roots. An option is to use the plastic, but leave large holes in it around the bushes. Alternatively you can combine the underlayments, placing landscaping fabric around the bushes and then covering the rest of the rock garden with heavy plastic. You’ll still leave holes for the bushes, but that space will be weed resistant because of the landscaping fabric.
Rocks, including river rocks and gravel, commonly serve as mulch to help keep weeds from finding a home in flowerbeds. When you cover a rock garden completely in rocks, you have built-in mulch support. Whether your garden has large boulders as part of its design or is low and flat, using color and texture for design, ensure the area is covered completely with small rocks serving as mulch. Scrape the rock mulch about 2 inches away from the trunks of the bushes to help prevent root rot and other fungal infections.
The Chemical Herbicide Option
A rock garden adds texture and color to a difficult area of a yard, such as a hillside, and it serves as a focal point. Adding bushes to a rock garden adds a touch of plant life that doesn’t require constant upkeep. When weeds pop up between the rocks, they mar the garden’s appearance, but one or more weed-control options – most notably, landscape fabric under the rocks – can be used to restore the site.
Because water passes through the landscape fabric under your rocks, holes in it need to be only large enough to fit around the bushes’ trunks. Cut lines in the fabric from its sides nearest to the holes for the trunks, so you can wrap the fabric around them. Covering the fabric with rocks helps hold it in place, although placing landscape staples every 2 feet or so along each edge of the fabric also helps.
Pulling weeds by hand is a traditional way to handle them organically, but other options exist that are easier on the back. Pouring boiling water over the weeds burns their leaves and kills the plants, as does pouring vinegar on them. Although salt is effective as a weedkiller, don’t use it in a rock garden that has bushes. Salt changes soil salinity and could kill your existing bushes while keeping future ones from growing.
Best Weed Barrier Under Rocks
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.
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.
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
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.
Even the best landscape fabric will break down after a few years, meaning weeds will grow again.
Cardboard or newspaper has to be replaced regularly, which can be time-consuming, but it could be recycled in your garden.
If you do choose plastic, select one with UV protection to prevent it from breaking down after a few years.
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.
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.