How Deep Should Mulch Be?
Before you can calculate how much mulch you’ll need to purchase, you’ll first need to decide how deep you intend to apply mulch. Most mulches are applied in 2- to 4-inch-deep layers; however, this can vary depending on your garden, your plants, the season, the mulch you’re using, and your goals.
In general, new gardens need more mulch than established beds, and loose and fluffy straw mulch is typically applied in deeper layers than denser mulches like shredded bark. And you’ll need to apply mulch in deeper layers if you’re intending to insulate plants in the winter and then remove the mulch before plants sprout in spring.
New raised vegetable beds: Apply about 3 to 4 inches of mulch.
Established raised vegetable beds: Refresh with 1 to 2 inches of mulch per year.
Flower beds: Apply about 2 to 3 inches of mulch in spring or fall.
Around trees and shrubs: Add 2 to 4 inches of mulch.
Pathways: Apply mulch in 3- to 4-inch layers to keep mulch lines from budging.
How to Calculate the Amount of Mulch You Need
Once you’ve decided how deep you’d like to apply mulch, it’s time to pull our your measuring tape and measure the areas you’d like to mulch. This is easy enough if your garden is square or rectangular in shape. However, if you’re dealing with an irregularly shaped garden, it’s usually easiest to break the bed into rectangular or circular shapes, measure each shape independently, and then add the measurements together to get the total area of your garden.
Once you know the dimentions of your garden space, use this calculation to determine how mulch you’ll need:
Garden length (in feet) X garden width (in feet) X intended mulch depth (in feet) = TOTAL MULCH VOLUME IN CUBIC FEET
For example: 10 feet (length) x 4 feet (width) x 3 inches or 0.25 feet (depth) = 10 cubic feet of mulch
Mulch is typically sold either in cubic foot bags or by the yard in bulk deliveries.
To determine how many bags of mulch to buy, divide the total cubic feet of mulch you calculated in the equation above by the size of the cubic foot bags you’d like to purchase. Most mulch bags are 2 cubic feet, so you’d divide the 10 cubic feet of mulch above by 2 to get 5 bags of mulch total. Adjust this calculation if the mulch bags you’re looking at are bigger or smaller in size.
To determine how many yards of mulch you’ll need, divide the total cubic feet of mulch you calculated above by 27 because there are 27 cubic feet in a yard. In this example, you’d need 0.37 yards of mulch to cover your garden.
Mulching Tips for Healthier Plants
Knowing how much mulch to order can help you avoid costly mistakes, like purchasing too much mulch. But if you’re new to working with mulch in your garden, keeping these tips in mind will make mulching even easier and help you save money too.
- Reduce mulch costs. Purchasing mulch in bulk by the yard is much more cost-effective than buying mulch bag-by-bag, and it reduces plastic waste too. If you want to save even more money, you can go the DIY route and make your own mulch with autumn leaves and a mulcher.
- Avoid rot. Placing mulch directly against plant stems can cause stems and trunks to rot and increase the risk of rodent issues. To avoid this, keep mulch lines at least 6-inches away from the trunks and stems of trees and other plants and never apply mulch in “volcanoes.”
- Refresh mulch regularly. Natural mulches break down over time, which can lead to weed problems if you don’t apply an annual application of mulch in spring or fall. Mulch colors look fresher during the growing season if you apply mulch in spring, but fall applications of mulch are better for insulating plant roots from the cold.
- Add extra weed protection. If you’re dealing with a major weed issue, laying a biodegradable layer of newspaper over your soil before mulching can help keep weeds down.
- Fertilize first. Whether you’re feeding plants with granular fertilizers, compost, or aged manure, it’s best to apply amendments to the soil before adding a fresh layer of mulch.
