To prevent weeds, choose a type of rock where the individual stones are no more than 2 inches (5 cm) long. Small stones and pea gravel lock together to make a strong weed barrier. Avoid large stones. The gaps between big rocks allow opportunistic weeds to sprout. Any small landscape rock will do an excellent job at preventing weeds, as long as it is installed correctly. Make sure to lay a barrier of water-permeable landscape fabric beneath your rocks to make the weed barrier as useful as possible.
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Do Landscape Rocks Prevent Weeds?
Landscape rocks are excellent for preventing weeds. A 3–4-inch deep (7.5–10 cm) layer of rocks laid over landscape fabric smothers weeds and prevents them from sprouting in your garden. However, if you do not use landscape fabric, the rocks will gradually be swallowed by the soil below. This will thin out your rock layer and give weeds a chance to grow.
- Landscape rocks are the best type of mulch for preventing weeds.
- Make sure to prevent weeds from growing in rocks by using these essential tips.
- Because rocks do not decompose, they create a longer-lasting weed barrier than organic mulch such as wood chips.
One of the top reasons to choose landscape rocks over organic mulch (such as wood chips or bark) is that the rocks do not decompose, so they do not need to be replaced. Organic mulches break down gradually, which reduces the mulch’s effectiveness as a weed-preventer. So, rocks create a much longer-lasting weed barrier than other mulches.
The #1 Best Landscaping Rock Type to Stop Weeds
The best rock for preventing weeds is any type of landscaping rock that is smaller than 2 inches long (5 cm). Pea gravel, lava rocks, and crushed stone all work equally well to smother weed seeds as they attempt to sprout. If appearance is your number one priority, you can choose colored pea gravel or river rocks. If you are trying to prevent weeds on a slope, use the best gravel for drainage.
- Any rocks smaller than 2 inches (5 cm) are great for preventing weeds.
- Choose a small rock type that fits your style and needs.
- Make sure to install a layer of water-permeable landscape fabric before pouring rock mulch.
- Add rocks over landscape fabric until the rock layer is 3–4 inches deep (7.5–10 cm).
- Avoid using large rocks—they allow sneaky weeds to sprout.
Large rocks and stones are not a good choice for preventing weed growth. Stones longer than 2 inches (5 cm) may not lock together and form a strong weed barrier. Gaps between larger rocks give a chance for weeds and grasses to sprout through your mulch. In addition, large rocks with sharp edges can tear through landscape fabric, which allows weed seeds to sprout more easily.
What Do You Put Under Landscaping Rocks to Prevent Weeds?
It is essential to put a layer of water-permeable landscape fabric down on top of the soil before adding a layer of rocks. If you are laying landscape fabric in a garden where you are already growing plants, cut an ‘X’ in the fabric where each plant is. Then, you can fold back the flaps of fabric and allow the plant to pass through. This makes it easy to install landscape fabric in any garden.
- This water-permeable landscape fabric must be installed under your landscaping rocks.
- Landscape fabric allows water to reach plant roots but physically stops weeds from sprouting up from the soil.
- A layer of landscape fabric stops dirt from mixing with your rocks, so weeds have nowhere to take root.
- If you do not lay landscape fabric, weeds will quickly invade your landscape rocks.
Once your landscaping fabric is covering the entire area where you want to suppress weed growth, keep it in place with landscape staples. Hammer these metal landscape staples through the landscape fabric and into the soil below. Drive in one landscape staple every 12 inches (30 cm) along the edges of the landscape fabric. Once this is done, you’re ready to add your weed-stopping rock mulch to your garden.
Do Rocks Prevent Weeds Better Than Mulch?
Rocks are more effective at stopping weeds than other types of mulch. Unlike organic mulches made from wood, nut hulls, or leaves, rocks do not provide any foothold where weeds can take root. Plus, some organic mulches (such as hay) can contain weed seeds, which may make a weed problem worse. It is extremely unlikely that rocks will contain any weed seeds, so you don’t have to worry that rock mulch will introduce new weeds to your garden.
- Rocks are longer-lasting and more powerful weed barriers than other types of mulch.
- Many types of organic mulch are soft enough that stubborn weeds can take root in the mulch.
- Some types of organic mulch may contain weed seeds—rocks do not.
- Unlike organic mulches, rocks do not provide soil nutrients.
The drawback of using rocks instead of organic mulch is that rocks do not break down and add nutrients to your soil. Decomposing wood, grass clippings, or shredded leaves boosts soil quality, which can help feed your lawn. Since rocks don’t provide this benefit, you’ll need to provide fertilizer for your garden in other ways.
Does River Rock Stop Weeds?
Small river rocks are a highly effective weed barrier. As long as the rocks are smaller than 2 inches (5 cm) long, they will lock together to form a nearly impenetrable barrier. So, if you like the look of river rocks, feel free to use them in your garden design.
- River rocks can be used to stop weeds.
- Small river rocks are the best choice, since they lock together and smother weeds before they can reach sunlight.
- Large river rocks may leave gaps where weeds can sprout.
Large river rocks are not the best choice for stopping weeds. If the stones are big enough that you can see gaps between them, then an opportunistic weed can sprout in that gap. However, even a layer of rock river rocks is a better weed-stopper than no mulch at all.
What is the Best Landscaping Rock for Preventing Weeds?
When choosing a rock type to use as a weed-prevention mulch, follow these tips:
- Any rock 2 inches (5 cm) or smaller will work excellently as a weed barrier.
- Large rocks leave gaps where weeds can take root.
- Rocks are more effective and longer-lasting than organic mulches, so they’ll stop more weeds longer.
- Before adding rocks to your garden, you must lay a layer of water-permeable landscape fabric on top of the soil.
- Secure the landscape fabric to the ground with landscape staples before adding rocks.
- Add 3–4 inches (7.5–10 cm) of rocks on top of the landscape fabric.
If weed prevention is the number one quality you look for in a layer of mulch, then landscaping rocks are the ultimate choice. They won’t break down or blow away. As long as they’re installed on top of landscape fabric, they won’t mix with the soil. So, your rocks will form a fantastic physical barrier that stops weeds.