How Much Mulch Do I Need? Here's The Easiest Way To Find Out

Adding a layer of mulch to your planting beds is the best thing you can do for your garden this year. Sure, you’ll get hot and weary long before you’re done with the chore. But mulch offers a huge payoff: Beautiful beds, fewer weeds, and healthier plants. Here’s everything you need to know before pulling out all of those gardening tools androlling up those sleeves (and putting on your garden shoes and gardening gloves!) and getting started.

What Is Mulch and What Does It Do?

Mulch—material made up of bark, leaves, or compost and used to cover soil—isn’t only about making your yard look neat and attractive. “One of its big benefits is that it helps conserve moisture in the soil by acting as a barrier to evaporation,” says John Esslinger, horticulture educator at Penn State Extension. “It also reduces the number of weeds and improves organic matter in soil, making your beds more productive over time.”

So, where should you mulch? Everywhere! Beds of annual or perennial plants, flowering shrubs, veggie gardens, and even containers benefit from mulch, which keeps the roots of new plantings moist as they’re getting established. And mulch protects tree trunks from string trimmers or mowers; just don’t mound it up directly against the trunk into a “mulch volcano.” That invites moisture and decay. “The organisms that break down mulch start working on the bark, too,” says Esslinger.

How Much Mulch Do I Need?

A 2" depth of organic mulch is ideal to retain moisture and keep down weeds, says Esslinger. But don’t go overboard: This is one time when more is not necessarily better. Plant roots need air to survive, and too deep a layer can suffocate roots and cause water to shed off the top of mulch instead of filtering through and soaking into the soil below.

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The maximum depth you should apply depends on the type: Finely textured mulch, like shredded hardwood, shouldn’t be more than 3" deep. Coarse textures, such as pine bark nuggets, allow more air movement so you can go up to 4" deep.

First, figure out the square footage of your bed. Multiply width by length for square or rectangular beds—or for round beds, multiply the radius (distance from the middle to the edge of the bed) by itself, and then multiple that total by 3.14.

Keep in mind that mulch is sold by the cubic yard. One cubic yard of the material covers a 324-square-foot area an inch deep. So, to determine your total, multiply your square footage by the depth in inches desired, then divide by 324.

Here's your formula: Square footage x desired depth / 324 = cubic yards needed.

Or, plug your measurements into an automatic mulch calculator. Lowe's has a good one, as does this website.

The Best Mulch to Use

Organic mulch means any type of natural substance that decomposes over time such as bark, wood chips, or pine needles. Straw is ideal for vegetable gardens. Replace mulch as needed, which is usually annually for fine or shredded types or every two to three years for coarser types like bark chips. Color is a personal preference.

Not all mulch is created equally. Avoid getting mulch from places such as your municipality’s transfer station, where yard waste is ground up and offered free to residents. For starters, you have no idea what’s in there. It may contain wood chips that are detrimental to other plants (for example, walnut trees contain a natural chemical that can inhibit growth). It also may include weed seeds and grass clippings that have been treated with herbicides. Stick with bagged or bulk product purchased from home improvement stores or nurseries.

Ready, Set, Mulch!

AMES 4-Tine Spading Fork

$40 at Amazon$50 at Walmart

Move mulch with ease with this pitchfork, which handles the material better than a spade.

Gardening Gloves

$42 at Terrain

The long cuff keeps mulch from spilling into your glove as it does with regular garden gloves.

Midwest Aluminum Landscape Rake

Shop at Amazon

Use this rake to smooth out your mulch in beds after installation.

Wheelbarrow

$218 at Walmart$139 at Home Depot

Haul mulch or tools around in this sturdy wheelbarrow featuring a flat-free tire that never needs air.