Compost vs Lava Rock
Side-by-side comparison of Compost and Lava Rock to help you choose the right gravel for your project.
Overview
Decomposed organic matter used as a soil amendment to improve soil structure, fertility, and water retention. Quality compost is dark, crumbly, and earthy-smelling. It adds beneficial microorganisms and nutrients that support healthy plant growth and improve poor soils.
Lava rock is a lightweight, porous volcanic stone commonly used in landscaping. Its rough texture helps retain moisture while allowing airflow to plant roots.
Common Uses
Compost
- ✓ Soil amendment
- ✓ Garden beds
- ✓ Lawn top-dressing
- ✓ Raised beds
- ✓ Tree and shrub planting
- ✓ Seed starting mix
Lava Rock
- ✓ Landscaping
- ✓ Garden beds
- ✓ Decorative ground cover
Pros & Cons
Compost
- + Dramatically improves soil structure and fertility
- + Increases water retention in sandy soils
- + Improves drainage in clay soils
- + Adds beneficial microorganisms
- + Reduces need for chemical fertilizers
- − Quality and composition vary widely between sources
- − Can be odorous when fresh
- − May contain weed seeds if not fully composted
- − Too rich for direct planting — must be mixed with soil
- − Settles significantly after application
Lava Rock
- + Very lightweight
- + Excellent moisture retention
- + Decorative appearance
- − Breaks down over time
- − Sharp edges
- − Can scatter easily
Cost Comparison
| Measure | Compost | Lava Rock |
|---|---|---|
| Per ton | $15 – $40 | $90 – $150 |
| Per cubic yard | $20 – $50 | $110 – $180 |
Sizes & Colors
Compost
Fine, crumbly texture when fully decomposed. Dark brown to black color. Should smell earthy, not sour or ammonia-like. Screened compost has been filtered to remove large uncomposted pieces. Mushroom compost is a byproduct of mushroom farming and is particularly nutrient-rich.
Lava Rock
Typically 3/4"–1.5" sizes. Red or black.
Published February 11, 2026
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