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Rock Mulch vs. Wood Mulch For Flower Beds, Which is Better?

Mulch is one of the most beneficial additions that you can incorporate into your flower beds. Adding mulch to your garden builds healthier plants by providing weed control, prevention of soil erosion, moisture and nutrient retention, and overall enhancement of your garden. This simple component can also save you endless hours of maintenance in your garden affording you less time watering, weeding, and even battling pests. This protective barrier can be composed of organic wood fines or bark mulch/ wood chip variety or an array of decorative rock varieties, but how do you choose between the two?

Green garden with rock and mulch

Factors to Consider when Choosing Mulch

The type of mulch that you select for your flower beds can have a measurable impact on your garden. Different kinds of mulch provide benefits and drawbacks that can impact the overall health of your garden and make or break your landscape. Find out if rock mulch or wood mulch made from wood fines or bark is right for your garden by considering all of these crucial factors.


When considering adding rock mulch or wood mulch your flower bed, an organic wood mulch is by far more affordable. Organic wood mulch costs much less than any variety of rock mulch or decorative stone. Often, you can even create the organic mulch yourself with compost or other materials from your yard. Organic mulch breaks down over time and deposits nutrients into the soil for greater plant health.

Rock mulch costs much more and is a more permanent solution. It will cost more to order and to deliver due to its weight. However, the minimal maintenance of decorative rock has an impact on the long-term expense.


Traditional mulch from wood fines and bark decomposes over time and requires periodic refreshing and replacement every year or two. Wood mulch starts out looking fresh and rich, but will fade over time detracting from the initial beauty that you were seeking.

Rock mulch does not decay and does require periodic replacement like a wood mulch does. Due to the weight of the rock, it will not wash away in heavy rain, and its natural color remains consistent over time and in all weather conditions.

Double level garden

Water Retention

Organic and rock varieties both provide beneficial soil cover, which helps with moisture retention and prevents soil soil erosion. The main difference between the two in this situation is that wood mulch, including other organic mulch varieties, both absorb the water and keep the soil underneath moist, which comes in handy, particularly when the climate is hot and dry.

Weed Control

Both wood mulch and rock mulch are beneficial in limiting weed growth in the open areas of your garden. The addition of weed tarp and mulch builds a nice barrier that limits the amount of sunlight that can encourage weeds to grow in addition to giving weed seeds blown into your garden a place to settle and germinate. Of course, weeds can still pop up and grow in the soil that collects between rocks or in the organic material of traditional mulch, so neither is foolproof when it comes to wiping out weeds entirely.

Flower garden with water feature

Soil Nutrition

Organic wood mulch made from wood fines or bark, provide a beneficial decomposition of organic matter, adding nutrients into the soil. This process is beneficial to your garden soil creating an excellent food source for beneficial soil microbes which in-turn, help feed the plant. This provides a renewable source of nutrients plants can use to help fight pests and diseases.

Pebbles, stone, and river rocks do not provide any renewable sources of soil nutrition.

Flexibility in Your Landscape

As a gardener, you may not think to consider how your choice of mulch can affect the flexibility that you have in their garden.

Organic mulches are easy to work with and allow you to shape your landscape with new perennial and annual plantings continually. The medium is very forgiving of the change that is often necessary or desired in the flower garden.

Rock mulch looks great in the flower garden; however, the heavy stone is incredibly labor-intensive to make changes with, move around or dig into for new plantings, reducing flexibility to change garden beds on a larger scale.

Heat Retention

While both organic and inorganic mulches provide insulation and protection for the soil around your plants in your flower beds, stone varieties may possibly do more harm than good.
Some rocks can retain too much heat, particularly the darker shades. As the stones heat up, the increase in temperature can be highly stressful on the plants in your flower bed, heating up the soil around the plants, drying out the soil instead of helping retain moisture. Ensuring there is at least a 3-4 inch layer of stone will help reduce heat absorption in the soil.

All Natural Planting Mix

Kellogg Garden Organics

All Natural Planting Mix

**Product not available in AZ, CA, HI, NV, UT. For a comparable product in these states click here.

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