The short answer
Use wood mulch around flowers, shrubs and vegetables, where you want healthy soil. Use rock (river rock or gravel) where you want something permanent and low-maintenance, such as along a foundation, in a dry creek bed, or in hot, dry yards with drought-tolerant plants.
| Wood mulch | Rock | |
|---|---|---|
| Typical depth | 2–3 in | 2–3 in (river rock 2–5 in, by size) |
| Weight per cubic yard | ≈600 lb | ≈2,700 lb |
| Lasts | 1–2 years, then top up | Many years |
| Soil | Breaks down and feeds it | No benefit |
| Heat | Keeps roots cool | Holds and reflects heat |
| Weeds | Good suppression, but seeds can sprout in it | Good with fabric underneath, but debris builds up between stones |
| Up-front cost | Low | High (often 2–4× per yard, and you need more weight delivered) |
Cost over five years
For a 200 sq ft bed at 3 in deep you need about 1.85 cubic yards. Mulch might cost a modest amount the first year and need about 1 in topped up each year after that. Rock costs more on day one but is usually a one-time purchase. Over five years the totals are often closer than people expect, so choose by what suits the plants and the look you want.
Where rock is a bad idea
- Around acid-loving shrubs and trees in hot sun, where stone heats the root zone.
- In beds you replant often. Rock is heavy and slow to move.
- Under trees that drop lots of leaves, since debris is hard to clean out of stone.
How much to order
For either one: area in sq ft × depth in inches ÷ 324 = cubic yards. Use the mulch calculator for bags or bulk yards, and the river rock calculator for tons of stone.
Frequently asked questions
Is rock or mulch better for weeds?
Both work well when they're deep enough. Rock over landscape fabric suppresses weeds for longer, but wind-blown soil and leaves collect between the stones over time and weeds grow in that.
Can I put rock over old mulch?
It's better to rake out most of the old mulch first. As the mulch rots, the rock sinks into it and weeds root in the compost layer.
Does rock attract termites less than mulch?
Rock doesn't feed termites and mulch does break down, so many people keep a 12–18 in strip of rock or bare soil against the foundation and use mulch further out.
Last reviewed 2026-11-14. Figures are typical averages; confirm with your local supplier.