Garden guide
How Deep Should Mulch Be? The Simple UK Guide
The quick answer
For most beds and borders, 5–7.5cm (2–3 inches) of mulch is ideal. That's deep enough to smother annual weeds and hold moisture, but not so deep it harms your plants.
Why depth matters
Under 5cm, light reaches weed seeds and they germinate straight through. Over 10cm, water can struggle to reach roots, slugs set up home, and stems rot where they sit against wet mulch.
The right depth for each job
Beds and borders: 5–7.5cm. Around trees and shrubs: 7.5–10cm, kept a hand's width away from the trunk. Veg patch paths: 10cm of coarse wood chip suppresses everything. Containers: 2–3cm — pots dry out fast and only need a top dressing.
Keep it off the stems
Whatever the depth, pull mulch back a few centimetres from plant stems and tree trunks. Constant damp contact is the one way mulch damages plants.
Working out how much you need
You need 10 litres per square metre for every centimetre of depth. A 20m² border at 5cm is 1,000 litres — about one and a half bulk bags. Our mulch calculator does the maths and prices the bags for you.