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.
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.
Best Weed Barrier Under Rocks
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.
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.
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.
You can also pour boiling water directly on the weeds to kill them, but wear long pants and close-toed shoes, to avoid burning yourself.
If you want to add a layer to block the sun (sunlight encourages weed growth), add a thick layer of newspaper or cardboard over the fabric.
How to Remove Weeds from Landscaping Rock
Now, put down a layer of underlayment. The heavy black plastic you may have seen in the past is not ideal. It decomposes quickly and corners start to stick up through the rock. Instead, top your bed with a good landscaping fabric. We highly recommend Hanes weed barrier fabric because, in our experience, it is the most weed-resistant.
If you are so inclined, use a good preemergent according to the product’s instructions. Next, install a steel edging border that is at least 3 inches high (4” is better). This will prevent weeds, grasses and plants from sending roots into your rock beds.
How to Prevent Weeds from Growing in Existing Landscaping Rock
Whenever you can, try to avoid using toxic chemicals in your yard and garden. You can successfully banish weeds from landscaping rock by pulling them but who wants to mess with that?