Depth depends on material
Coarse bark, fine compost and mineral mulch behave differently. Follow supplier guidance and account for whether the goal is moisture retention, appearance or weed suppression.
Keep stems clear
Piling mulch against trunks and crowns can trap moisture. Leave an appropriate clear zone around plants.
Refresh by measuring
Measure remaining depth before adding more. Topping up to a target is usually better than repeating the full original application.
Practical checklist
- Remove established weeds before mulching.
- Do not block drainage or air vents.