Don’t rock your landscape

Rocks are fine as landscape accents, but gravel-gilded grounds aren’t a good gamble in Texas’ terrain.

Excessive heat and a severe lack of rain have taken a toll on many San Antonio landscapes, particularly those laden with lush lawns. So, it’s no surprise that one of the most common questions we get is about a rebate for rocks. After all, they don’t require any water.

When used strategically and effectively — as a border, around an A/C unit, in between a flagstone patio or walkway, or as a “dry creek” feature to correct drainage issues on your property — rocks rock!

But using them in place of foliage simply because they don’t need any watering whatsoever isn’t the solution. Let me tell you why.

Rocks generate heat.

River rock and decomposed granite absorb the sun’s radiation and retain it far into the night. Compared to organic mulches, rock can reach 140-170 degrees in the summer while woodchips or pine bark is a relatively 80-85 degrees. I think we can all agree we don’t need any additional heat during our south Texas summers.

They increase stormwater runoff.

The impact may not be as significant as a parking lot or street, but rocks are also an impermeable surface, and in large quantities will increase stormwater flow, thus increasing flooding. Likewise, smaller rocks, gravel, and decomposed granite will collect at drains and grates, blocking stormwater from entering the drainage sources.

They offer no nutritional value.

River rock does not provide nutrition or carbon, the gasoline of the soil ecosystem. Without carbon, fungi, protozoa, and other microfauna and flora cannot survive, and plants will eventually suffer or die.

Rocks are not maintenance-free.

One of the most frequent responses we hear concerning rock is that they’re less maintenance. In the short-term perhaps, but rocks need to be blown or cleaned weekly to prevent debris from collecting. If debris accumulates, nature takes its course and plants begin spreading, even if there’s a weed barrier.

They’re not a main component of xeriscape.

Rocks are never mentioned in the 7 principles of xeriscape. In fact, in it’s simplest form a xeriscape is minimal lawn, native flowering perennials and shrubs, mulch and other soil amendments, and pervious patios or decks.

While flagstone and paver patios are good components of an ideal landscape, entire yards or beds of river rock and gravel don’t make sense. And they don’t look so great either.

If less maintenance is what you’re really after, use rocks in shady areas that will naturally suppress sun-loving weeds. For areas near the street, select larger sized stones that are less likely to wash away and clog up storm drains.

Picture of Mark Peterson
Mark Peterson
Mark A. Peterson was a conservation project coordinator for San Antonio Water System before retiring. With over 30 years of experience as an urban forester and arborist, Mark is probably the only person you know who actually prunes trees for fun. When not expounding on the benefits of trees and limited lawns, you're likely to find him hiking San Antonio's wilderness parks or expounding on the virtues of geography and history to his friends.
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