What is Mulch? 

Close-up of grey mulch wood chips

If you want to protect your soil, mulch has you covered. Mulch is a material — from leaves and wood chips to rubber and fabric — that is spread over your soil, and it’s bursting with lawn benefits. It’s used to reduce erosion, prevent weeds, insulate soil from sudden temperature shifts, and retain soil moisture for healthier roots.

Mulch is like an enchanted cloak for your lawn that can transform it from drab to dazzling. Let’s go through what mulch is and how it can cast a spell (the good kind!) on your lawn.

Mulch’s natural roots

Who invented mulch? Humans can’t take credit for this one. Nature has been conjuring up its own mulch long before lawns began. 

Forests are the original organic mulch-makers. Leaves and branches blanket the forest floor, providing nutrients to the soil as they decompose, spurring tree root growth, and keeping the ecosystem healthy and balanced.

The mulch we see in garden stores mimics the natural conditions of the forest floor. In harsher, less-forested environments like cities and suburbs, mulch gives your plants a taste of home.

Organic vs. inorganic mulch

There are two different types of mulch: Organic and inorganic. The big difference? Organic mulch can decompose and inorganic mulch cannot.

Organic mulch is made of natural materials (like wood, pine needles, and grass clippings) that break down as they age and need to be replaced every few years. Though organic mulch can be a hassle to reapply, it gives your soil and roots a whole spellbook of magical nutrients. Because of this, landscaping professionals prefer it to inorganic mulch.

Inorganic mulch can be either natural (river rocks and gravel) or synthetic (rubber and plastic), but it won’t break down over time. If you want to avoid the frustration of routinely replacing your mulch, it’s a fantastic option, but it won’t give your soil the benefits of organic nutrients. 

Best types of organic mulch for your lawn

Though spreading organic mulch every few years can be an annoyance, it doesn’t have to be a financial burden. You can use your own natural yard waste as healthy, nutrient-rich mulch. 

  • Leaves: A 2- to 3-inch layer of coarsely shredded leaves will control weeds and decompose quickly, giving your lawn a strong nutrient boost. Leaf mulch is a great choice for general yard use: It works well on turf, in vegetable gardens and flower beds, and around trees and bushes. 
  • Tree bark: Tree bark mulch can be sold shredded or in larger “nugget” form, in many varieties of hardwood and softwood. Nuggets are especially popular and readily available as a decorative lawn addition. A healthy 2-3 inches of bark mulch will resist soil compaction and wind erosion on slopes and around trees. 

Pro Tip: For plants that thrive in acidic soil, pine bark is an excellent choice.

  • Grass clippings: A 2- to 3-inch layer of grass clippings prevents weed growth and decomposes quickly, providing plenty of nutrients to your soil. Just make sure you’re using dry grass: Wet clippings can form a mat and prevent water from filtering into the soil. Avoid using grass clippings treated with herbicide, as harsh chemicals can harm your plants. 

Pro Tip: Want to use your own grass clippings as mulch? A mulching mower will recycle your clippings right back onto your lawn.

  • Pine needles: Pine needles (AKA pine straw) interlock to stay in place, so they’re perfect for slopes and ridges. They’re long-lasting (two to four years) and release a pleasant aroma as they age. A 3- to 4-inch layer is perfect in garden beds and around trees and shrubs that prefer acidic soil. 
  • Arborist wood chips: A 1- to 3-inch layer of wood chips is an aesthetically pleasing, inexpensive choice for pathways, around trees, and in perennial gardens. Wood chips also have a long lifespan: They’ll last two to three years. 

Pro Tip: When wood-based mulches decompose, they use nitrogen, so you’ll want to apply fertilizer to increase nitrogen availability for your plants.

  • Aged sawdust: Aged sawdust is a favorite for acid-loving shrub crops like blueberries and rhododendrons. As it decomposes, it can rob soil of nitrogen, so apply fertilizer directly after you spread sawdust. You’ll want to apply aged sawdust 2-3 inches deep.
  • Straw: For vegetable gardens and newly seeded lawns, a 3- to 4-inch layer of straw is an excellent choice. It’s cheap and decomposes quickly, improving the soil as it goes. You can choose from a variety of straw types, from wheat and timothy to oats, rye, and barley. Just be mindful of weeds and unwanted plants: Straw often contains grain and weed seeds, which you won’t want in your garden. 
  • Compost: Compost is the head wizard of the mulching world. It’s a nutrient-rich mixture of decomposing organic matter, from table scraps to fallen leaves. A 2- to 3-inch layer of compost will fertilize your soil and give your plants an enormous growth boost. Compost is perfect for vegetable gardens, flower beds, trees, and shrubs.

Pro Tip: You can buy compost at your local garden store or you can make it an eco-friendly, money-saving DIY project. 

Organic mulch also can still be alive! Don’t worry, it’s not an “Attack of the Zombie Plants” situation. Ground covers like liriope, pachysandra, periwinkle, and clover prevent erosion and soil compaction, insulate and conserve moisture, and suppress weeds. They’re often referred to as living mulch or cover crops. 

To decide which organic material is the perfect witch’s brew for your lawn, check out “Types of Mulch.”

Best types of inorganic mulch for your lawn

For rock gardens, rain gardens, pathways, and playgrounds, inorganic mulch is an attractive, weed-resistant lawn addition that requires minimal maintenance. 

  • Gravel, pebbles, and river rocks: A 1-inch layer of gravel or rocks is an excellent form of weed control that will resist soil compaction and wind erosion. Plus, rocks look great around driveways and footpaths. You can choose colors and textures to compliment your home and landscape.

Pro Tip: If you have acid-loving plants, stay away from limestone gravel. Limestone will raise your soil’s pH level.

  • Black plastic landscape tarp: A layer of black polyethylene will prevent weeds in flower and vegetable gardens, but proceed with caution. Black plastic doesn’t allow for the flow of air or moisture, so root rot can become an issue. Cut holes in the plastic sheeting to encourage the flow of moisture, and bury it underneath a more decorative, organic mulch (like wood chips or pine needles). 
  • Landscape fabric: Landscape fabrics (AKA geotextiles) suppress weeds while also encouraging a free flow of air and moisture. Make sure you anchor your landscape fabric to prevent movement. Then, apply a top layer of decorative mulch for visual appeal. If a weed pops up, pull it out immediately so it doesn’t get embedded in the fabric. 
  • Reflective metallic mulch: Reflective mulches look like they’re straight out of a sci-fi movie, but they’ll repel pests like nobody’s business. Shiny and silvery, these mulches signal to insects like aphids that they should “keep flying.” You’ll need to cut holes in the mulch for planting and install a drip irrigation system to ensure the roots get plenty of water. 
  • Rubber mulch: Recycled rubber from tires improves your soil’s moisture retention, controls erosion, and keeps soil warm in the winter. Plus, it’s sturdy and resists decomposition. However, zinc toxicity from tires can inhibit plant growth and some experts warn against the use of rubber as a mulch. 

12 benefits of mulch

1. Keeps soil moist.

Mulch locks water into the soil, both improving water infiltration and reducing evaporation so you don’t have to water as frequently. In hot summer months, mulched plants can tolerate drought better than their mulch-less peers.

2. Prevents soil compaction. 

Mulch decreases foot traffic so your soil can breathe. Uncompacted soil stays airy and nutrient-rich, which reduces your need to aerate.

3. Prevents weed and grass competition.

Trees and shrubs flourish without root competition from grass, weeds, and other low-growing plants. Plus, you won’t have to sweat it out weeding near your trees.

4. Protects trees from mower damage.

Mowing, trimming, and weed whacking around trees and bushes can stress your plants and injure their roots and trunks. Mulch keeps them comfortable and protected.

5. Increases root growth and spread. 

Mulched plants extend their roots into the surrounding mulch, while mulch-less plant roots are contained to the soil area. 

6. Reduces erosion.

Mulch keeps soil firmly in place, so particles of sediment won’t crust on the surface of your lawn or flow into the storm drain during heavy rain. This also benefits the environment by decreasing the amount of polluted runoff that enters your local aquatic ecosystem.

7. Protects against soil-borne diseases.

Fungal and bacterial diseases can do a number on your grass and garden, causing discoloration, wilting, and plant death. Mulch prevents soil splashing, so soil-borne diseases don’t make contact with plant leaves. 

8. Adds visual appeal.

Landscape artists often include mulch in their yard designs for added curb appeal. Mulch is a beautiful accent piece around trees and in places where it’s difficult to grow grass. 

9. Keeps soil temperatures stable. 

Mulch acts like a warm blanket in winter and a cool towel in summer, protecting your soil against sudden temperature fluctuations. This is especially important for root health: With mulch, roots don’t have to go through stressful cycles of freezing and thawing. 

10. Improves soil composition and texture (if organic).

As organic mulch decomposes, it breaks down clay soils and increases the moisture-retaining capacity of sandy soils. Mulch naturally amends your soil to be more hospitable to plant growth. 

11. Increases nutrient levels (if organic).

As organic mulch decomposes and moves downward, it improves the nutrient levels of the topsoil. Organic mulch (especially compost) increases your soil’s fertility, feeding your soil a cornucopia of healthy food.

12. Attracts earthworms and beneficial microorganisms (if organic). 

Nutrient-rich, organic mulch is a playground for beneficial worms, insects, and microbes. If you don’t have earthworms already, adding a layer of compost will attract them to your lawn. Earthworm burrows improve water infiltration, naturally aerate your soil, and reduce compaction. Plus, worm castings (excrement) add even more nutrients to your soil. 

How to spread mulch

1. Clean debris. 

Remove twigs, sticks, and rocks from the area where you plan to apply mulch. Your mulch should have strong contact with the soil surface to give roots what they need. 

2. Thoroughly weed your area. 

Weeds can become embedded in mulch as they grow, which makes weeding through mulch aggravating. Start with a clean slate by fully weeding before you spread your mulch.

Pro Tip: If the area is not around a tree or shrub, mow grass on the lowest mower setting to get your area nearly grass-free. Then, kill the remaining grass by sheet mulching (laying newspaper to smother the grass). 

3. Spread mulch. 

Apply 1-4 inches of mulch over your desired mulching areas. Don’t go overboard: Too much mulch can harm your plants and soil. 

4. Water thoroughly (if mulch is organic). 

Give the area 1 inch of water to set your mulch in place. 

Beware of too much of a good thing: Applying more than 4 inches of mulch can damage the root systems of the plants you’re trying to help. Too much mulch will inhibit the flow of oxygen to roots, which can cause disease and plant death. 

  • Finer mulches (half an inch or smaller in size) should be applied at a maximum depth of 2 inches. Otherwise, their small size will hamper oxygen from reaching the root zone.
  • Coarser, larger mulches like tree bark chips can be applied as deep as 4 inches. Use less mulch if your soil does not drain well. 
  • Do not mulch around tree trunks: Keep the root flare (where the base of the tree meets the ground) clear of mulch to prevent inner bark death and fungal diseases. 

FAQ about mulch

1. When should I use mulch?

While you can apply mulch at any point in the year, it’s best to mulch in early to mid-spring, near the beginning of the growing season. With warmer temperatures comes root growth, so mulch in spring is the perfect time to give plants a nutrient surge. 

2. How much mulch do I need? 

Mulch is normally measured in cubic yards. The amount of mulch you need depends on the size of your area and how deep you want your mulch to be. 

Calculate the volume of mulch you need by multiplying the area (in square feet) by your desired depth (in fractions of a foot), and then dividing by 27. 

Let’s say you want to mulch a part of your yard with an area of 150 square feet, and you want your mulch to be 2 inches deep.

Convert your desired depth of 2 inches to feet. 
2 inches / 12 inches=0.17 feet

Multiply your area in square feet by your desired depth in feet to find the cubic feet of mulch needed. 
Area in square feet x Desired depth in feet = Cubic feet of mulch needed
150 square feet x 0.17 square feet =25.5 cubic feet of mulch needed

You’ll need 25.5 cubic feet of mulch to fill your area.

There are 27 cubic feet in a cubic yard, so to convert, divide by 27.
Cubic feet of mulch needed / 27 cubic feet per cubic yard =Cubic yards of mulch needed
25.5 cubic feet of mulch / 27 cubic feet per cubic yard=0.95 cubic yards (rounded up)

You’ll need 0.95 cubic yards of mulch. If you’re buying mulch at a garden store, you’ll want to round up and purchase a full cubic yard.

3. How do I apply mulch around a tree? 

Mulching around a young tree (less than 10 years old) is “the single best practice” you can do to give that tree a healthy jumpstart, according to the Kansas State Master Gardener extension

Begin by spreading mulch 3-6 inches away from the tree trunk. Remember, it’s crucial that you avoid mulching directly around the tree trunk. Think of your mulch ring like a donut: You want a hole (not a mountain of dough) in the middle.

Extend your mulch ring 3-6 feet around your tree. For sustained growth, you’ll want the widest ring possible. As the tree grows, expand the ring’s diameter so roots get the full benefit of mulch.

Spread your layer of mulch 2-4 inches deep. 

Replace mulch yearly. First, pull away the mulch that has settled at the tree trunk. Then, check your mulch depth: You may need to remove old mulch before adding new mulch to your desired depth. Your mulch layer should never be higher than 4 inches. 

The magic of mulching

Has mulch bewitched you? It may be time to summon some in your own lawn. You can buy mulch at your local home improvement store or garden center, or you can concoct your own at home. 

Want a real lawn wizard to transform your lawn? Call a local lawn care pro for all your magical mulching needs. 

Main Photo Credit: MatteoSunbreeze | Pixabay

Maille Smith

Maille-Rose Smith is a freelance writer and actor based in New York. She graduated from the University of Virginia. She enjoys watching theatre, reading mysteries, and listening to psychology podcasts. She is an orchid enthusiast and always has a basil plant growing in her kitchen.