GardenCalc.uk · Free UK Field Guide 03
The UK Mulch Timing & Depth Guide
Which mulch, how deep, and when — to lock in water and starve the weeds.
Which mulch for which job
| Mulch | Best for |
|---|
| Bark / wood chip | Borders, paths, shrubs — long-lasting, smothers weeds |
| Compost / rotted manure | Veg beds & borders — feeds the soil as it breaks down |
| Gravel / grit | Drainage + drought beds, Mediterranean & alpine plants |
| Straw | Strawberries & veg — keeps fruit clean, holds moisture |
| Leaf mould | Woodland / shade beds — free if you save autumn leaves |
How deep + when
- Depth: 5–7.5cm (2–3 inches). Thinner won't stop weeds; thicker can suffocate roots.
- When: autumn (lock in warmth + moisture for roots) and spring (after the soil warms, before the summer dry).
- Always mulch onto moist soil — mulching bone-dry ground just keeps it dry.
The one mistake to avoid
- Keep mulch off stems and trunks — piling it up ("mulch volcanoes") rots the bark and invites disease. Leave a clear collar.
The £-saver
Bark in bulk bags costs a fraction of small sacks. Many councils give away wood chip, and your own autumn leaves make free leaf mould.
📐 How many bags you need in 10 seconds
gardencalc.uk/mulch-calculator