Rock beds look clean and appear to be a one-time purchase. Mulch looks rich but has to be refreshed. In South Florida the decision is less about appearance than about what happens to soil temperature and moisture underneath.
What mulch does well
- Holds soil moisture, which cuts irrigation demand in the dry season
- Keeps root-zone temperatures down through the summer
- Breaks down into organic matter that improves sandy Florida soil
- Suppresses weeds while it stays at the right depth
- Costs less up front than decorative rock
What rock does well
- Does not blow or wash away in heavy storms
- Never needs annual replacement
- Works well in drainage swales and high-runoff areas
- Suits cactus, succulent and modern xeriscape plantings
- Will not attract termites near a structure
The heat problem nobody mentions
Rock absorbs and radiates heat. In a full-sun South Florida bed, rock can drive soil temperatures high enough to stress the root systems of tropical shrubs and perennials. Plants in rock beds frequently need more water, not less, and often struggle for reasons the homeowner never connects to the ground cover.
Our general recommendation
Use mulch in planted beds where living plants need cool, moist soil, and refresh it annually to a depth of two to three inches. Use rock in drainage areas, along foundation drip lines, and in deliberately designed low-water plantings.
Keep both pulled back a few inches from trunks and stems. Piling either material against a trunk traps moisture and invites rot — the single most common bed mistake we correct.
