It costs twice what wood chips do — and it's the cheapest mulch you'll ever buy: the one material you lay down once
There is a special genre of purchase I like to call the subscription you didn't know you signed up for. Gym memberships. Printer ink.
And — hear me out — wood mulch. Those chips look cheap at $25 to $100 a cubic yard, right up until you remember they decompose and demand replacing every year or two, forever, until you die or sell the house, whichever comes first.
The break-up material
The alternative is lava rock. Actual chunks of cooled volcano, sold in red, black, and brown, in sizes from pebble to "small boulder," running $50 to $180 per cubic yard. Yes, roughly double the wood-chip price. And yes, it's still the cheaper option, because you buy it exactly once. It does not rot. It does not compost itself into the soil. It just sits there, doing its job, for decades.
"Lava rock is excellent as a mulch because it lasts a long time," landscape designer Lisa Hallett Taylor told LoveToKnow, pointing out that unlike bark, it simply doesn't break down.
The rock earns its keep beyond immortality, too:
- It's heavier than chips, so a windy day or a downpour doesn't redistribute your landscaping into the neighbor's yard
- That weight also makes it a legitimate erosion-control material on slopes
- It's porous — water passes straight through to the soil, which makes it a darling of drought-friendly xeriscaping
- Weeds struggle to establish in it, especially with a fabric barrier underneath
The fine print (there's always fine print)
Before you fill a truck bed: lava rock adds essentially zero nutrients to your soil, because rocks famously do not decompose. Installation is a workout — it's heavier to haul than chips, the edges are sharp enough that heavy gloves are non-negotiable, and you'll likely want weed fabric under it and edging around it so it stays where you put it.
And there's the vibe question. A cottage garden dressed in volcanic rubble looks like a misunderstanding; this is a material for modern, structured, or desert-leaning yards. But if your aesthetic allows it? Lay it down once, cancel the mulch subscription, and spend every future spring doing literally anything else.
