What To Know About Using Gravel Mulch in the Garden

Even if it’s not always much to look at on its own, gravel has so many uses in the garden. It can be decorative, like when I used it to top my pots of succulents, or functional, like when it’s blended with soil to improve drainage for plants that don’t like excessive moisture around their roots.

Top-dressing flower beds with gravel mulch is becoming increasingly popular for several reasons. It pairs nicely with alpine plants in rock gardens and with plants that like it hot, from desert aloes and agaves to prairie Echinaceas and grasses. But they’re not for everyone or every garden. Here’s why you should or shouldn’t use it in your garden.

We talked to Seattle-based designer Lisa Bauer about how she uses various gravels for pathways, patios, to level pots on the ground, and in the right situations, as mulch in planting beds.

About the Expert

Lisa Bauer is an award winning designer who owns Chartreuse Landscape Design in Seattle, WA. She holds an Associate’s Degree in Landscape Design and Ornamental Horticulture and is a Certified Professional Horticulturist (CPH).

What Is Gravel Mulch?

Mulching is the practice of covering the soil around plants to protect the soil and roots of plants from water loss and extreme temperatures, both hot and cold. You can mulch with many materials, with natural wood chips being the most common, but gravel offers a different look. Bauer applies 1/4″-3/8″ clean, crushed gravel mulch 1.5″ – 2.5″ deep on beds around plants. “Clean” gravel is free of “fines” – bits smaller than #/4″ – and thus drains well and compacts less readily.

She also passes on pea gravel – it rolls away too easily. She prefers to use gravel mulch in areas away from large trees or shrubs that drop leaves or debris, ideally with an edging border to keep the gravel in place.

Gravel mulch myths

There are some misconceptions about gravel mulch. Here’s a breakdown of everything you need to know.

Pros of gravel mulch

Improves aeration and drainage

Gravel may be a good choice for your garden, depending on the plants you are growing. “Gravel is a good mulch for plants needing sharp drainage, especially drought-tolerant or low-water plants,” says Bauer. They’re not ideal for plants that need more consistent water.

Expands your design options

Gravel is a versatile design element that suits modern designs or gardens with a dry, Western, or Mediterranean aesthetic perfectly. Bauer says, “It can look quite nice and comes in many colors,” which you can choose to play off the surroundings. The colors often pop against garden foliage for a striking contrast.

Durable

Because gravel doesn’t decompose, gravel mulch doesn’t need replacing as frequently as arborist mulch, perhaps every 2-6 years, depending on foot traffic and whether edging is used, says Bauer. It also is less likely to blow or float away in storms than lighter-weight mulches.

Cons of gravel mulch

Not ideal for thirsty plants

If you are growing plants that prefer to be evenly moist, arborist chips would be a better option.

More expensive and harder to haul

At the front of the project, Bauer says, gravel “is heavier and more costly to install,” than organic mulch materials like wood chips.

Still needs replacing

While gravel may not decompose like wood chips, it does settle – and migrate.

“It can work its way down into the subsoil,” says Bauer, “so you will have to replenish it as you would organic mulch,” though not as often as arborist chips. Loose gravel rolls around, and is picked up by shoes and passing paws. You can mitigate the migration by installing an edging to the bed to corral the gravel, making it last longer.

Does not improve the soil

While arborist wood chip mulch feeds and improves the soil structure as it breaks down, gravel doesn’t offer that same benefit, so it doesn’t nourish the soil and surrounding ecosystem.

Requires cleaning and weeding

Gravel mulch may help discourage weed seeds in the soil beneath from germinating, but the big issue is wind-borne weed seeds, says Bauer. They can fly in and sprout from fragments of leaf litter between the gravel. Bauer recommends using a leaf blower to keep the area clear of litter. To save time clearing, avoid using gravel mulch under mature trees or shrubs that drop significant leaves or debris.

FAQs

Do plants grow well in gravel mulch?

Most plants benefit from the temperature-moderating effects of mulch, and plants that prefer their roots to be drier especially appreciate the aeration of gravel mulch. In contrast, plants that like more moisture may need more supplemental water with a gravel mulch.

Do rock flower beds attract snakes?

It depends. Tightly-knit gravel or river rock is less inviting to snakes than loose wood mulch or large rocks

What is the best rock for mulching?

Bauer uses 1/4″-3/8″ clean, crushed gravel mulch because it drains better than gravel with fines and rolls less than pea gravel.