Three inches — that is the depth that reliably blocks the light weed seeds need to germinate. On established beds that still hold an inch of old mulch, a 2-inch refresh gets you back to the target. Thinner than that and sunlight sneaks through; much deeper and you risk smothering shallow roots. Keep the mulch pulled a few inches back from stems and trunks either way.
Coverage at weed-blocking depth
| 1 yard at 3 inches | ~100 sq ft |
| 3 yards at 3 inches | ~300 sq ft |
| 5 yards at 3 inches | ~500 sq ft |
Measure your beds now, before spring germination starts — then shop bulk mulch and size the order with the material calculator, rounding up to the next half yard.
