How much mulch do I need for a 5x20 flower bed?
Check it with your own numbers
Open the Mulch Calculator with these values
| Length | 20 ft |
| Width | 5 ft |
| Depth | 2 in |
| Mulch needed | 0.62 yd³ |
| 2 ft³ bags | 9 |
| 3 ft³ bags | 6 |
A long, narrow bed
A 5x20 bed is the classic foundation planting along the front of a house. It is 100 square feet, the same as a 10x10, but the shape changes how you work it. At 2 inches deep you need 16.7 cubic feet, which is 0.62 yd³, 9 bags of the 2 ft³ size or 6 of the 3 ft³ size.
Why 2 inches here
Foundation beds are usually established, with shrubs that already shade much of the soil. A 2-inch top-up each spring keeps the bed looking fresh without building up a thick layer against the house. Go to 3 inches only if the bed is new or the old mulch has broken down to bare soil.
Keep mulch off the siding
This is the detail that matters most on a bed against a wall. Leave a 6-inch strip of bare soil or gravel between mulch and the foundation. Mulch against wood siding or sill plates holds moisture and gives termites a covered path to the house. Many pest control companies will flag it during an inspection.
Check the grade
Soil plus mulch should still slope away from the foundation. If years of mulch have raised the bed level above the bottom of your siding, rake out the old layer before adding new.
Working a 20 ft bed
- Lay the bags out every 2 ft along the bed's length before you open any of them. You will see right away if you are short.
- Use a hand cultivator around shrubs instead of a full rake. Narrow beds leave no room to swing.
- Rubber or rock mulch is sometimes used along a foundation to avoid the termite issue. It costs more but never needs topping up.
Round up or down?
If you are between bag counts, round up. A partially used bag keeps for next year if you fold the top over and keep it out of the sun.
Related questions
For other sizes, use the full Mulch Calculator or browse all answers.