Library · Field, beds & planting
Mulch Calculator.
Mulch Calculator
How much mulch for any area and depth. Plus cost comparison across 12 mulch types and what each is best for.
Mulch type comparison
| Mulch | Best for | Pros | Cons |
|---|---|---|---|
| Wood chips (arborist) | Trees, shrubs, paths, perennial beds | Free from arborists; long-lasting (2-3 years); builds soil | Ties up surface N briefly during decomp; not for annual veg roots |
| Bark mulch (cedar/cypress) | Ornamental beds, foundations | Decorative; pest-deterrent oils (cedar); long-lasting | Expensive; cedar/cypress harvesting concerns |
| Straw / hay | Vegetable beds, strawberries, potatoes | Cheap; quick decomp adds OM; weed-suppressing | Hay seeds weeds; straw is preferred; fire risk; rodent habitat |
| Pine needles | Acid-loving plants (blueberries, azaleas) | Slightly acidifies soil; cheap if local | Slow decomp; flammable |
| Compost | Vegetable beds (top layer) | Feeds soil; boosts biology; ideal for annuals | Decomposes fast (1 year); some weed seeds; cost |
| Leaves (shredded) | Vegetable beds, perennials | Free; excellent soil-building; carbon-rich | Whole leaves mat and exclude air; shred first |
| Grass clippings | Vegetable beds, paths | Free; high N (good for tomatoes/heavy feeders) | Mat down; herbicide risk if from treated lawn; smell |
| Living mulch (clover) | Orchards, perennial beds, paths | Self-renewing; N fixation; pollinator forage | Competes with main crop if not managed |
| Black plastic / landscape fabric | Warm-season crops; weed-heavy areas | Soil warming; total weed kill | Anaerobic soil over time; microplastics; replaces yearly |
| Biodegradable plastic | Organic-compatible weed barrier | Tills in at end of season; warm-season benefit | Expensive; partial breakdown variable |
| Stone / gravel | Permanent xeriscape, paths, around trees | Doesn't decompose; no annual replacement | Heat-reflecting (bad for shallow roots); no soil contribution |
| Cardboard / paper | Sheet mulching new beds | Free; suppresses weeds for 6-12 months | Single-season; tape/labels must be removed |
Application rules
- Don't pile mulch against tree trunks ("mulch volcanoes") — invites rot, rodents, and disease. Pull mulch back 2-3" from the trunk.
- Apply to moist soil. Mulch over dry soil keeps soil dry; over wet soil keeps it moist. Water thoroughly first.
- Don't bury seedlings. Wait until plants are 4-6" tall before mulching, or pull mulch back when planting.
- Refresh, don't pile. 1-2" annual top-up after decomposition; don't accumulate 6+ inches over years.
- Carbon-rich mulches steal surface N. Don't till fresh wood chips into soil; surface application only. Add a thin compost or N source layer underneath if needed.
- For weed control: 4-6" depth required to suppress germination. 2-3" only slows annual weeds.
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