Stoned in the Garden: The Case Against Stone Mulch

Good soil conservation practices should start in our own backyards.  This post is my take on a futile and frustrating mulching practice that persists for no reason other than that it briefly looks nice.

Some folks might assume because I’m a geologist that I’d be a fan of stone mulch on the landscaping beds around my house.  When we purchased our house eight years ago, I found it to be a novelty that one of the previous owners had put down stone mulch on all of the beds.  My opinion of stone mulch has grown over the past eight years.  From neutral to What the hell were they thinking?!?!?

Starting two years ago, I’ve been gradually trying to reclaim our landscaping beds, one bed at a time.  Two years ago in order to plant our butterfly garden in front of our house, I raked and shoveled dozens of wheelbarrows full of the three-quarter- to one-inch diameter stone out of the front bed and started a pile of the unwanted gravel at the end of my driveway.  Last year, I reclaimed a bed on the side of our deck to plant an herb garden.  This summer I reclaimed a few other beds around our deck and patio.  And last Saturday, after spending six hours engaged in mind-numbing and back-wrenching raking and shoveling, I knew that blogging about stone mulch was probably the only thing I could do to ease the frustration of how much of my free time I’ve invested over the past two years trying to rid my landscaping beds of the scourge of decorative crushed stones.

Why Bother?

Any pragmatic casual gardener who reads this rant will undoubtedly think, “Why bother?”  Fair question, my casual gardening friends; however, I consider myself more than a casual gardener.  I consider myself a deliberate gardener.  Before I grow too old and weary to do anything more than tend my vegetable garden, my goal is to have nearly all of my landscaping beds covered with native perennials that I will not have to tend year after year.  I want my beds to be brimming with perennials so that there won’t even be any bare ground showing that will need mulch, and thus no bare ground for weeds to come up among the expansive native perennials.  I can dream, can't I?

Drawbacks to Stone Mulch

Here are the drawbacks to stone mulch that might not be very apparent when someone is getting a sales pitch from a landscaping contractor.

Plant matter that falls into the spaces between stone mulch
decomposes into soil and gives weeds a growth substrate.

Weed fabric is installed on the bare soil before the stone mulch is laid down.  That might sound like a fool-proof way to weed-proof, but I’d estimate it’s good for five years tops in a temperate climate.  After five or so years, stone mulch accumulates enough leaf matter falling from above to develop brand new soil in the interstitial spaces between the stones.  Then you get weeds growing in the new soil between the stones and sending roots down into and through the weed fabric.  Weeds can’t grow up through the weed fabric from below, but both water and weed roots can get through from above the weed fabric.

My other big gripe with stone mulch is that it’s very arduous to plant anything in it.  In a bed with organic mulch and a weed fabric, it’s no big deal to dig in with a spade and make holes for bulbs or plants.  Planting in stone mulch requires extensive raking to clear even a small patch in which to penetrate the weed fabric and reach the underlying soil.  I would imagine that even casual gardeners would become frustrated by the difficulty inherent in trying to plant anything through two or three inches of stone mulch.

The way it should look.

And of course, when using stone mulch, your beds are not getting the benefits of organic mulch such as:  returning nutrients to the soil, maintaining soil moisture and temperature, and blocking light from the soil to prevent weed seedlings from becoming established (sunlight can partially penetrate into the spaces between stone mulch).  In addition, beneficial critters like my toad friends cannot burrow through stone mulch and weed fabric to hibernate for the winter. I want to do everything I can to encourage natural insect controls, like toads, to live in the beds around my house.

This is one of my toad friends that lives under our deck.

 The Rest of the Story

I still have a lot of work ahead of me in my battle to reclaim my landscaping beds from stone mulch, although I’m quite pleased with each individual bed that I reclaim.  I’m less than halfway through the battle, but I’m hoping it doesn’t take me another two years to finish.  Actually, the biggest problem I’m facing right now is what to do with all of the stones I’ve removed thus far and have yet to remove from my beds.  I estimate I’ve got about a four-ton pile so far. I’m open to suggestions, but I’m guessing I might have to resort to Craig’s List.

Any takers?