GardenCalc.uk · Free UK Field Guide 03

The UK Mulch Timing & Depth Guide

Which mulch, how deep, and when, so you 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

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.

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.