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Rock Vs. Mulch: Detailed Guide for Landscaping

Rock Mulch Perfect Area

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When you’re planning out new landscaped beds or hardscape features, you’ve got a choice to make: Rock vs mulch.

Landscaping rocks are classified as inorganic mulch, since they don’t break down over time. Rock mulch comes in many varieties, including lava rock, pebbles, river rocks and crushed stone. 

Wood-based mulch is an organic material, meaning that it will decompose into its basic elements over time. Some of the most common wood mulches include hardwood blends, cedar and cypress. 

Both landscaping rocks and wood mulch have their pros and cons, and each is better suited to certain uses.

With their sturdy nature and heavy weight, rocks can be a fantastic solution for several landscape challenges.

Here are 7 landscaping areas that can benefit from a layer of rock mulch:

1. High-Traffic Areas

Thanks to its strong structure, rock can easily support any extra weight. Additionally, using rock mulch in pathways can provide a safe, stable surface to walk across.

On the other hand, wood mulch can quickly lose its fresh appearance in landscape beds that receive frequent foot traffic. After repeated trips across its surface, wood mulch can wear away, get crushed or sink into the soil.

2. Pool Edging

There’s a reason that rivers, lakes and oceans have rocks lining their bottoms, banks and shores.

Even after epic splashing events, rock won’t wash away or migrate into your pool water the way loose mulch can. This can help you keep your pool water cleaner with less work on your part.

3. Areas Prone to Standing Water

Do you live in an area with a high water table? Maybe you have a low-lying area that always floods after a rainstorm. In these instances, river rocks or decorative pebbles can be a lifesaver.

Mulching wet areas with pine bark nuggets or cypress mulch often leads to frequent clean-ups. Not only that, but you may also have to completely replace your mulch more often, driving up your gardening costs.

Using rock mulch is a great strategy for maintaining your water-prone landscape with less effort and long-term cost.

4. Established Trees and Shrubbery

Rock naturally absorbs and holds heat from the sunlight, thereby warming the soil underneath. Although this characteristic may help encourage plant growth in early spring, it can also make the soil too hot and parched for some plants during the summer.

As a result, rocks have the potential to damage young plants or those with delicate root systems.

After a few years of growth, most healthy trees and shrubs have established a fairly extensive root system. Since they reach so deeply into the earth, older plants are unlikely to feel any ill effects from rock mulch.

5. Areas at High Risk for Wildfires

Since they are non-flammable, rocks can be a safer choice if you live in a region threatened by wildfires.

Unfortunately, landscaping rock alone can’t divert a wildfire away from your house. Nevertheless, taking precautionary steps whenever possible is usually a good idea.

6. Drought Resistant Plantings

Certain plants tolerate or even prefer warm, dry soil. For these plants, rocks can help produce ideal growing conditions while also reducing maintenance work for you.

These are just a few examples of plants that thrive in dry soil:

  • Lavender
  • Cacti
  • Trumpet Vines
  • Artichoke

7. Bordering a Hardscape

Hardscaping involves using non-living decorative elements in your outdoor space. These are a few popular hardscape features:

  • Decks
  • Fountains
  • Gazebos
  • Brick, concrete or stone patios
  • Retaining walls
  • Fencing

A rock mulch border can be a fitting backdrop for these bold, decorative elements.

When Should You Avoid Rock Mulch?

Landscape rocks have much to offer in terms of appearance and maintenance. However, they’re not appropriate for these three types of garden beds:

  • Vegetable Gardens
  • Fruit Orchards
  • Annual Flowerbeds

Rocks aren’t suited to these types of plants for several reasons:

  1. Rocks don’t break down or enrich the underlying soil with essential nutrients. Fruits, vegetables and annuals need high amounts of nutrients to produce abundant crops and blooms.
  2. Rock absorbs sunlight and holds heat. Vegetables and annual flowers tend to have shallow roots that are more vulnerable to burning and temperature fluctuations.
  3. Moisture readily evaporates from the gaps between rocks, leaving your shallow-rooted plants thirsty.
  4. Once you’ve placed rock mulch, it’s heavy to move. Planting annuals in rock-covered beds can be a big chore every spring.

In these situations, compost mulch, grass clippings, shredded leaves or hardwood mulch are far superior.

We’ve put more mulch suggestions for various types of garden and landscape beds in our Mulch Mastery guide. Stop on by for more details!

Maintaining Rock Mulch

Easy maintenance is one of the top draws of using rock mulch. With the proper initial precautions and a commitment to minimal upkeep, you can look forward to years of beauty from your landscape rocks. 

Use a Weed Barrier

As opposed to wood mulch, rocks have more nooks and crannies for weeds to find their way through. Prevention is the best strategy to keep weedy ugliness from invading your landscape. 

Before laying the first rock, cover the bare soil in your landscape bed with a physical weed barrier. A couple of good barrier options include garden fabric or black plastic.

These materials block sunlight to prevent any existing weed seeds from germinating. Additionally, these barriers keep new weed seeds from reaching the soil. 

Clean Stones Periodically

Wind will likely blow dust and dirt onto your landscape rocks over time. If left unattended, weeds may take root in this top layer of dirt. 

Make washing your rock mulch a part of your spring and fall home maintenance routine.

Although washing rocks sounds like a tedious task, it really isn’t. Spraying your rocks off with a hose or pressure washer should be enough to keep stones fresh and weed-free. 

Final Thoughts

Rock mulch isn’t right for every garden or landscape bed. Nevertheless, in appropriate settings, rock mulch can deliver lasting beauty with next-to-no maintenance effort on your part. 

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About Erinn Witz

Hi! I’m Erinn, a Midwestern gal who’s just as interested in honing my gardening skills as you are. I’m here to show you that if I can do this growing thing, seriously, YOU can too! 

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